tag:blogger.com,1999:blog-51424615119791213422012-03-18T01:38:39.356-07:00Kumarnoreply@blogger.comBlogger3131100tag:blogger.com,1999:blog-5142461511979121342.post-20472606153646743832012-03-14T05:46:00.001-07:002012-03-14T05:47:38.414-07:00

Researchers have finally found out how sulfa drugs—the first class of antibiotics ever discovered—work at the molecular level. Sulfa drugs work by binding and inhibiting a specific enzyme called dihydropteroate synthase (DHPS). This enzyme is critical for the synthesis of folate, an essential nutrient. Mammals get folate from their diet, but bacteria must synthesize this vitamin. Sulfa

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-77885808312986127262012-03-13T01:48:00.000-07:002012-03-13T01:48:15.060-07:00

The ability of one gene to influence the expression of another gene, or even a group of genes. The existence of epistasis should not be surprising if one considers biochemical pathways. Several different genes are involved in such pathways, and if an early step in the pathway is blocked, then the precursor for a later gene is not made, and thereby the action of the later gene is disrupted.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-15013554459452752522012-03-06T01:58:00.000-08:002012-03-06T01:58:58.664-08:00

Worldwide, liver cancer is the third cause of death caused by cancer, falling in behind lung (1.4 million deaths) and stomach cancer (740,000 deaths) at around 700,000 deaths. For the first time, researchers have discovered a special type of molecular regulator called a micro-RNA (miR-124) that could be used someday as a treatment for liver cancer. The same team also found a mechanism in mice

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-50333313702582340462012-03-02T01:41:00.002-08:002012-03-02T01:41:46.305-08:00

As B cells grow into a clone in response to antigen, they may rearrange their DNA once again. For example, a B cell that has assembled a complete gene for the H chain of IgM (µ), may cut the gene on the 3´ side of the assembled V-region segments and move the assembly to the 5´ side of another of its CH gene segments. Now the cell begins to make a different class of antibody, such as IgG or IgA.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-81605090533271511032012-02-24T07:12:00.000-08:002012-02-24T07:12:50.950-08:00

Men and women can seem like they’re from different planets sometimes. Hormones help drive those differences. A new study shows how genes pass on the message. Hormones are the body's signaling molecules. They affect many aspects of development and biology. Researchers have long known that the sex hormones, such as estrogen and testosterone, drive certain differences in behavior between men and

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-57051149660583096362012-02-24T07:04:00.000-08:002012-02-24T07:04:11.359-08:00

Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth. In addition, in many tissues they serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential either to remain a stem cell

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-8078745712284236052012-02-23T04:14:00.000-08:002012-02-23T04:14:05.830-08:00

A massive effort to sequence and compare 29 mammalian genomes has shed new light on the “dark matter” of the genome, the over 98% of DNA that doesn’t code for proteins. The DNA that lies outside of gene sequences was once called “junk DNA.” But researchers now know that these non-coding regions have important biological functions. Many disease-causing mutations have been found in these areas, and

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-34131766435522782002012-02-20T05:57:00.000-08:002012-02-20T05:57:41.185-08:00

Why can some people make it through difficult times with little trouble while others crumble under the same circumstances? A new study suggests that the answer lies—at least in part—in your genes.Scientists have long known that people with certain psychological traits, or resources, can fare better in challenging situations. Three of the most widely studied psychological resources—optimism,

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-40396148159160554912012-02-20T05:50:00.000-08:002012-02-20T05:50:51.800-08:00

New research reveals that Parkin, a protein linked to some cases of early-onset Parkinson's disease, regulates how cells in our bodies take up and process dietary fats. The finding suggests that defective Parkin may contribute to early-onset Parkinson's by changing the amount and types of fat in the body.Parkinson's disease, a complex, progressive and currently incurable neurological disorder,

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-74861873930212188572012-02-20T05:40:00.000-08:002012-02-20T05:40:55.732-08:00

Resveratrol, a compound found most famously in grapes and red wine, seems to ward off several age-related diseases. However, its mechanism of action has been elusive. Researchers have now found a direct molecular target for the compound. People can develop a variety of metabolic diseases as they age, including type 2 diabetes and heart disease. In animal studies, severely restricting calories

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-31017600354266532082012-02-08T05:21:00.000-08:002012-02-08T05:21:44.470-08:00

Two related studies revealed gene activity in the brains of people of different genders and ethnicities, from fetal development to old age. The accomplishment provides a broad foundation for understanding both normal brain development and what goes awry in mental disorders.  Messenger RNAs, or transcripts, are transient copies of genes that carry instructions to the protein-making machinery

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-37173004856313677502012-02-08T05:08:00.000-08:002012-02-08T05:08:39.003-08:00

“While transplantation is a life-saving therapy for patients with end-stage organ disease, it also puts recipients at an increased risk for developing cancer, in part because of medications administered to suppress the immune system and prevent rejection of the organ,”. Organ transplant recipients have a high risk of developing 32 different types of cancer, according to a new study. Future

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-69668961782805993482012-02-05T07:12:00.000-08:002012-02-05T07:12:13.966-08:00

Scientists have developed a noninvasive technique that uses light to selectively wipe out cancerous cells in mice without harming surrounding tissue. With further research, this novel method might eventually be used to treat tumors in humans. The 3 major types of cancer therapy—surgery, radiation and chemotherapy—effectively destroy cancerous tissues, but tend to damage normal tissue as well.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-75073857295877911422012-02-05T07:07:00.000-08:002012-02-05T07:07:57.722-08:00

A lubricating layer made of graphitic carbon naturally forms in the joints of metal-on-metal hip implants, a new study shows. This solid layer, produced within the body, is more like an industrial lubricant than joint fluid. The finding may help researchers design longer-lasting metal-on-metal hips for treating arthritis and other joint disorders. The most common hip implants are made of metal

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-63786253630274736042012-02-03T23:26:00.000-08:002012-02-03T23:26:57.839-08:00

Researchers have devised a gene transfer technique in mice that, with a single injection, protects the immune cells that HIV targets. With further development, the approach may prove effective at helping to prevent HIV infection in people. Most vaccines work by triggering the immune system to produce antibodies to help beat back infections. But a vaccine for HIV has been elusive. Proteins on the

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-29417851725910612962012-02-03T23:19:00.000-08:002012-02-03T23:19:55.624-08:00

Scientists have identified a genetic mutation that causes cold temperatures to trigger allergic reactions—a condition called cold urticaria. Cold urticaria is an allergic disease in which cold temperatures bring itchy, sometimes painful hives, episodes of fainting and potentially life-threatening immune reactions. Earlier research had tied the disease to immune system cells called mast cells.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-1476596337122560712012-02-03T08:19:00.000-08:002012-02-03T08:19:34.047-08:00

A single dose of an experimental gene therapy boosted production of a missing blood-clotting factor in people with hemophilia, a new study shows. The therapy might give patients a long-term solution for preventing dangerous bleeding episodes. Hemophilia is a rare, inherited disorder in which blood is unable to clot normally. As a result, people with hemophilia tend to bleed more than others

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-82405354426249389032012-02-03T08:12:00.000-08:002012-02-03T08:12:39.829-08:00

Since the discovery of the microscope, scientists have tried to visualize smaller and smallerstructures to provide insights into the inner workings of human cells, bacteria and viruses. Now, researchers have developed a new way to see tiny structures within viruses.Conventional cryo-electron microscopy (cryo-EM) has allowed researchers to image the surface of viruses in great detail. But

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-4857671030354801212012-01-28T21:11:00.000-08:002012-01-28T21:11:33.329-08:00

In 1933, the American Clark and Gollan kept some mice immersed in a liquid which flooded their lungs and should have killed them. But they stayed alive. This fluid was an emulsion of a fluorocarbon in water. These fluorocarbon molecules link up with significant quantities of oxygen present in the water. This showed the beginnings of the invention of the blood substitute. In 1967, the American,

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-84898621954111155902012-01-28T21:03:00.000-08:002012-01-28T21:03:35.218-08:00

The French doctor Velpeau made some observations on aneurysms. He pricked a needle into an aneurysm and noticed the formation of a clot. In 1835, the French doctor Charles Gabriel Parvaz invented the hypodermic syringe for injecting ferric chloride. The syringe was made up of a silver cylinder and the lid of the pump body could be screwed down; the cylinder had a nozzle to which the cannula

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-39066209972174969842012-01-28T03:44:00.000-08:002012-01-28T03:44:36.304-08:00

Your heart beats around 100000 times a day, 36500000 times a year and over a billion times if you live beyond 30 The lightest organ in the human body is the lung. Adult lungs have a surface area of around 70 square metres!  The brain uses over a quarter of the oxygen used by the human body Humans have a stage of sleep that features rapid eye movement (REM). REM sleep makes up around

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-83595405026306528112012-01-21T06:13:00.000-08:002012-01-21T06:13:25.915-08:00

The amount of information in human DNA is roughly equivalent to 12 sets of The Encyclopedia Britannica, an amazing 384 volumes worth of detailed information that would fill 48 feet of library shelves! But the size of a DNA molecule is only two millionths of a millimeter thick. In order for there to be anything resembling a language it must meet the following criteria; an alphabet or coding

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-80005159577220372012012-01-21T06:11:00.000-08:002012-01-21T06:11:43.339-08:00

A new study(study published in the journal Proceedings of the National Academy of Sciences) that was recently published sheds more evidence to what many have been saying for a long time, that DNA does not control the body or predestine you to being overweight, ill, sick, weak or anything else, but that the majority of our health and destiny lies within our own power. The men underwent three

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-13792842143615891172012-01-21T06:09:00.000-08:002012-01-21T06:09:08.682-08:00

The old traditional methods of criminal investigations gave forensic experts a tedious job. They relied only in witnesses and visual presentation. But how about the unseen cases of murders and other criminal acts? Because of the advancement of technology and human knowledge, forensic experts collect evidence around the crime scene including hair remains, liquids like saliva, semen and others.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-86839829577857506012012-01-21T06:04:00.000-08:002012-01-21T06:04:29.387-08:00

A newly released study has found that drinking tea results in a 37% reduction in breast cancer risk for women under the age of 50, an age in which breast cancer can be particularly virulent. Another recent study has shown that tea drinking reduces risk of endometrial cancer. These results add to the pile of data showing tea is one of the healthiest beverages a person can drink.Whether it is

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-2691543227996714982012-01-19T11:04:00.000-08:002012-01-19T11:04:32.277-08:00

1. What is Cochlear microphonics ? A. It is the electrical potential generated in the hair cells of organ of Corti in response to acoustic stimulation, called as cochlear microphonic. 2. What is axon reflex ? A. Axon reflex is a response brought on by peripheral nerve stimulation. It is also known as Hunter reflex reaction as it causes vasodialation and loss of body heat from extremities. 3.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-28258332890667021532012-01-13T03:36:00.001-08:002012-01-13T03:36:09.342-08:00

Create recombinant medicines for treatment of human disease, forensic analysis of samples including crime scene evidence or paternity tests, mammalian cloning, modification of traits of agriculturally important species. There are many additional possibilities.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-82178517464862516812012-01-13T03:35:00.001-08:002012-01-13T03:35:51.344-08:00

We could find out the number of human genes, develop an understanding of how those genes work to control the functions of human cells and the entire human body, learn how mutations in those genes cause disease. We could develop better diagnoses and treatments for genetic diseases. We could learn more about our relationship to other organisms and the mechanisms of evolution. There are

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-32799782416542427122012-01-07T10:36:00.000-08:002012-01-07T10:36:27.789-08:00

Reverse genetics is an approach to discovering the function of a gene by analyzing the phenotypic effects of specific gene sequences obtained by DNA sequencing.  This investigative process proceeds in the opposite direction of so-called forward genetic screens of classical genetics. Simply put, while forward genetics seeks to find the genetic basis of a phenotype or trait, reverse genetics seeks

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-42573288195182497952012-01-07T10:12:00.000-08:002012-01-07T10:12:23.247-08:00

In the 25 years since they were first discovered, introns have puzzled molecular biologists because of their uncertain function and mysterious origin. Introns are non-coding DNA sequences that reside inside a gene, splitting it into discrete units called exons. The resulting disruption of coding sequence continuity would wreak havoc in protein assembly if eukaryotic cells did not dispose of

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-61388981269115885912012-01-07T09:57:00.000-08:002012-01-07T09:57:02.462-08:00

A theory that holds that introns are extremely ancient characteristics of genes and that early genes were created through the intron-mediated shuffling of exons. The theory has existed since the late seventies. An uncompromising version of the theory, in which all introns were considered to be ancient, dominated the early work. However, in the late eighties and early nineties evidence arose that

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-9136535034650863472012-01-07T00:02:00.000-08:002012-01-07T00:02:39.551-08:00

Anthocyanin pigments, stored in the vacuoles of petal cells change color with pH (acidity). The Japanese Morning Glory, Ipomoea tricolor var. Heavenly Blue, changes color from purple to blue in the early hours of the morning A section of the petal (B) shows the transition in color. Notice the change in cell volume (C) and pH (D) accompanying the color change. This is a caused by the induction of

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-83477996914775302512011-12-31T02:13:00.000-08:002011-12-31T02:13:14.179-08:00

The step one plus RT-PCR ( 96 well platform, 4 color system, veriflex sample blocks) use fluorescent-based PCR reagents to provide 1) Quantitative detection of target nucleic acid sequences using real time analysis, 2) Qualitative detection of targets using post-PCR (end point) analsyis, 3) Qualitative analysis of the PCR product (achieved by melt curve analysis that occur post-PCR) and 4) Time

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-67314762126256608402011-12-31T00:21:00.001-08:002011-12-31T00:21:52.221-08:00

When disease associated proteins occur in a cell they are broken into pieces by the cells proteolytic machinery. Cell proteins become attached to antigen fragments and transport them to the surface of the cell, where they are "presented" to the bodies defence mechanisms. These transport molecules are called the Major Histocompatibility Complex (MHC) proteins. Without these, there would be no

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-68634280223707768952011-11-01T08:21:00.000-07:002011-11-01T08:21:42.663-07:00

Although it is not necessary to do so, we can make a simplifying assumption that both human cells and bacterial cells have the shape of cubes. Since the bacterial cells are I /25th the length of the human one, as many as 25 x 25 x 25 will fit inside. (Picture a large cube and start stuffing it with the little ones, 25 rows of 25 on the bottom layer, and 25 such layers); 25 x 25 x 25 =15,625.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-12585309334139042082011-10-07T02:51:00.000-07:002011-10-07T02:51:43.660-07:00

We grow; we reproduce; we think. How did it all begin? Our universe began 10 to 15 billion years ago . The initiating event is described as the big bang.During the first 3 minutes after the big bang, as the universe began to expand, energy density reduced enough to allow protons, neutrons, and electrons to form. Some of the very lightest of the elements also formed, including some helium and

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-42621283985752614962011-09-23T05:07:00.000-07:002011-09-23T05:07:22.997-07:00

Question Define horizontal gene transfer. What problems does it cause for evolutionary biologists? Answer Horizontal gene transfer, also called lateral gene transfer, is the transmission of genetic information across species boundaries. Horizontal gene transfer takes place frequently in bacteria, through transformation and phage-mediated transduction. In eukaryotes, horizontal gene transfer

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-24401160038590001052011-09-23T05:06:00.001-07:002011-09-23T05:06:30.866-07:00

The molecular clock estimates the rate at which nucleotide changes take place in a DNA sequence.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-76150030253857742412011-09-23T05:06:00.000-07:002011-09-23T05:06:15.329-07:00

Question Briefly describe differences among the distance approach, the maximum parsimony approach, and the maximum likelihood approach to the reconstruction of phylogenetic trees Answer   The distance approach relies on the degree of overall similarity between phenotypic characteristics or gene sequences; the most-similar species are grouped together. The parsimony approach tries to

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-75189080062809249562011-09-23T05:05:00.000-07:002011-09-23T05:05:08.825-07:00

First, a geographic barrier splits a population into, say, two groups and prevents gene fl ow between the groups on either side of the barrier. The two groups then evolve independently. Through natural selection, genetic drift, and mutation the two groups become genetically different. These genetic differences lead to reproductive isolation, and the two groups will have undergone allopatric

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-82544912719223754772011-09-23T05:04:00.001-07:002011-09-23T05:04:47.126-07:00

The biological species concept defi nes a species as a group of organisms whose members can potentially interbreed with one another other but are reproductively isolated from members of other species. One problem with this concept is that it does not apply to asexually reproducing organisms. Another is that, in practice, most species are defi ned by phenotypic or anatomical differences, and

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-78488016276218896152011-09-23T05:04:00.000-07:002011-09-23T05:04:29.391-07:00

Question: What is the key difference between the neutral-mutation hypothesis and the balance hypothesis? Answer Neutral-mutation hypothesis: Most molecular variation is adaptively neutral.Balance hypothesis: Most genetic variation is maintained by balanced selection, favoring heterozygosity at most loci.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-27102833079408644792011-09-23T04:57:00.000-07:002011-09-23T04:57:04.606-07:00

Question: As a measure of genetic variation, why is the expected heterozygosity often preferred to the observed heterozygosity? Answer Because the expected heterozygosity is independent of the breeding system.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-72477216088553124162011-09-23T04:54:00.001-07:002011-09-23T04:54:15.082-07:00

Mutation Recombination

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-65695330227646383132011-09-14T13:31:00.001-07:002011-09-14T13:31:44.350-07:00

A major advantage is that it leads to the synthesis of groups of functionally related enzymes, usually from a single mRNA transcript. Since a functional pathway must be activated in terms of all of its components, the operon affords an all-or-none response that serves efficiency. The control mechanisms existing for turning on or turning off the operon make the operon sensitive to those changes in

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-85225563261376680922011-09-14T13:28:00.000-07:002011-09-14T13:28:43.661-07:00

In order for DNA to initiate the formation of RNA for subsequent translation, it must first unite with an RNA polymerase. The site for RNA polymerase attachment on the DNA is called the promoter. The operator lies within the promoter region (or overlaps it) so that attachment of the RNA polymerase is blocked when the repressor is present. In the presence of an inducer (lactate or a closely

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-62201179792247627912011-06-15T07:12:00.000-07:002011-06-15T07:16:14.317-07:00

For those who like to drink cold water,It is nice to have a cup of cold drink after a meal. However, the coldwater will solidify the oily stuff that you have just consumed. It will slow down the digestion. Once this 'sludge' reacts with the acid, it will break down and be absorbed by the intestine faster than the solid food. It will line the intestine. Very soon, this will turn into fats and lead

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-10583030197091593142011-04-28T12:32:00.001-07:002011-04-28T12:32:54.594-07:00

Packaging: The tight packaging of the DNA around the histones is achieved because the histones shield the negatively charged phosphate groups from each other. Otherwise the DNA would repel itself and could not fold up tightly.Transcriptional control: The tight packing of DNA makes it less accessible for transcription that requires open access to the base sequence. Transcription factors (proteins)

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-50536396532974982652011-04-28T12:31:00.001-07:002011-04-28T12:31:37.251-07:00

Proteins whose folding must occur in the membrane, such as integral membrane proteins, need to be translated within the organelle so they can dock with the membrane in the folding process. They often have to be embedded with a surface on the inner face of the organelle membrane. These proteins cannot be synthesized in the cytoplasm and then exported to the organelle, as the folding environment of

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-716187150326855672011-04-28T12:29:00.000-07:002011-04-28T12:30:19.258-07:00

There Genomes, like prokaryotic genomes, are circular and usually very efficient, containing no repetitive sequences or introns. The ribosomes used in translation are closer to those in the bacterial protein synthesis system than in the eukaryotic one; e.g., 12S and 16S rRNAs are used. Other clues include the number of membranes surrounding the organelle; some organelles have more than one

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-20843262739181891182011-04-28T12:28:00.000-07:002011-04-28T12:29:15.112-07:00

Noncoding RNAs can recruit proteins to certain RNA sequences. These proteins can then modify the RNA (as occurs with snoRNA), regulate the stability of specific sequences by orchestrating their destruction or protecting them from destruction, altering the rate of translation by binding to 5′-UTR or 3′-UTRs, and localize specific sequences within the cytoplasm.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-24707710577869659872011-04-28T12:27:00.001-07:002011-04-28T12:27:42.380-07:00

RNA acts as an interim molecule that can amplify gene expression much better than directly translating the protein from the DNA. An interim template offers multiple levels of regulation that proceeding directly from DNA to the protein does not. By regulating the stability of the mRNA, the up-regulation of more copies of the protein is ensured. It also allows for greater flexibility when

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-45372119212760272902011-04-28T12:25:00.000-07:002011-04-28T12:26:19.902-07:00

Noncoding RNA is RNA that is generated by transcription from DNA but that is not translated into protein.It includes the major structural RNAs: rRNA and tRNA as well as small nuclear RNA (snRNA), small nucleolar RNA (snoRNA), microRNA (miRNA), and short interfering RNA (siRNA).

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-3523223065228147692011-04-28T12:23:00.000-07:002011-04-28T12:24:12.782-07:00

Those DNA molecules that have the most copies of a given sequence will reanneal fastest in solution because there is a higher probability of encounter between complementary sequences. Hence more complex single-copy sequences take the longest to reanneal. The probability of a long sequence encountering its complementary sequence in a mixture of sequences in a given time is small because of its

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-16989114289613188752011-04-28T12:21:00.000-07:002011-04-28T12:22:11.815-07:00

What are the consequences of other deaminations to the genetic code? SOLUTION While adenine and guanine also contain amino groups that can be spontaneously hydrolyzed from the nucleobase, the resultant bases are hypoxanthine and xanthine, respectively. Neither of these bases is typically found in the genetic code. Thus a system of molecular machinery has evolved whereby they are identified and

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-52901557250876605402011-04-28T12:19:00.000-07:002011-04-28T12:20:39.117-07:00

Bacteria usually do not methylate cytosine residues and do not use methyl CpG as a means of regulating gene expression. Bacteria typically methylate adenine residues, which protect genomic DNA from restriction by restriction endonucleases and tag the parent strand during mismatch repair.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-20983033057121387942011-04-28T12:17:00.001-07:002011-04-28T12:17:40.265-07:00

Deamination of cytosine yields uracil, which is thought to be why DNA has evolved to contain methyl uracil (thymine), to enable the correction of this chemically inevitable corruption of the coded message. However, there are regions of the genome that contain significantly higher proportions of methyl cytosine, often preceding a G in the sequence. These regions are associated with gene silencing

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-27627653779634966302011-04-28T12:15:00.000-07:002011-04-28T12:16:24.975-07:00

With degeneracy (different codons that code for the same amino acid) of the genetic code it is possible to have different base sequences in a gene and yet code for the same sequence of amino acids. In coding for leucine, e.g., the RNA codons for leucine are CUU and CUA which correspond to 33.3% (G + C), while its other two RNA codons are CUC and CUG and these are 66.7% (G + C). If the first codon

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-87224752630710226502011-04-28T12:13:00.000-07:002011-04-28T12:14:01.697-07:00

In prokaryotes a large fraction of the genome contains coding sequences, hence large sections are copied into RNA. Thus the transcriptome of a bacterium will reflect the base composition of its respective genome. However, only one strand of DNA is copied at any one time, and some sequences are copied far more often than others. The promoter regions, although quite short in bacteria, are rich in A

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-45029236275573973842011-04-28T12:11:00.000-07:002011-04-28T12:12:20.116-07:00

The fraction of the total DNA used for coding proteins in eukaryotes is much less than in prokaryotes. Many eukaryotic species have nuclear DNA with an order-of-magnitude more base pairs than are required to encode all the different proteins. Note also that the size of the genome has little correlation with the complexity of the organism. This observation is referred to as the C-value paradox.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-85600392209331955392011-04-28T12:08:00.001-07:002011-04-28T12:10:20.326-07:00

The use of 32P (radioactive) to label DNA and RNA for Southern and northern blotting was a major technical advance. One of the earliest exploitations of the unique phosphorus content of nucleic acids was the Waring-blender experiment (first performed by Alfred Hershey and Martha Chase). This groundbreaking experiment proved that DNA (and not protein) was responsible for genetic information flow

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-91132052045930687352011-04-28T12:06:00.001-07:002011-04-28T12:07:07.686-07:00

It must be stable, with a structural backbone that is resistant to chemical attack from cellular components.It must have scope for variation with a range of different side chains that are covalently linked to the backbone.The side chains must be stable and distinguishable by other molecules through selective binding.There must be a chemical process for copying the polymer that faithfully

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-20004038278874869192011-04-28T12:02:00.000-07:002011-04-28T12:05:45.405-07:00

The first process is DNA replication: This can extend to duplicating the whole genome. It occurs immediately prior to cell division and is necessary for the transfer of genetic information from one generation to the next. The fidelity of the copying process must be as high as possible. There is little room for errors in this process, as these will be copied perhaps trillions of times in the

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-69320726365878261452011-04-21T10:26:00.000-07:002011-04-21T10:29:13.795-07:00

Cyclin-Cdk complexes provide internal control for cell cycle decisions. Cells in multicellular organisms must divide only when appropriate. They must respond to external signals, controls called growth factors. Some cells respond to growth factors provided by other cells. Platelets release platelet-derived growth factor, which diffuses to the surface of cells to stimulate wound healing.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-67141640116692378642011-04-21T10:19:00.000-07:002011-04-21T10:24:28.749-07:00

The movement phases of chromosomes are designated pro-metaphase, metaphase, and anaphase. During pro-metaphase, the nuclear lamina disintegrates and the nuclear envelope breaks into small vesicles permitting the fibers of the spindle to “invade” the nuclear region. The spindle microtubules then associate with kinetochores. These are called kinetochore microtubules. The microtubules from one pole

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-44216856176687381752011-04-21T10:15:00.000-07:002011-04-21T10:18:51.633-07:00

Dominant gain-of-function mutations in proto-oncogenes and recessive loss-of-function mutations in tumor-suppressor genes are oncogenic. Among the proteins encoded by proto-oncogenes are positive-acting growth factors and their receptors, signal-transduction proteins, transcription factors, and cell-cycle control proteins. An activating mutation of one of the two alleles of a proto-oncogene

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-32948798360619177022011-04-21T10:10:00.000-07:002011-04-21T10:14:00.603-07:00

The latent provirus is invisible to the immune system.The virus undergoes rapid mutational changes in antigens during replication which eventually overwhelms the immune system.The population of helper T-cells eventually declines to the point where cell-mediated immunity collapses. Researchers are not entirely sure why this occurs. Secondary infections characteristic of HIV infection develop (

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-50528237968500564842011-03-19T19:29:00.000-07:002011-03-19T19:33:59.075-07:00

The nucleus is the chief organelle involved in cellular reproduction. During the life of the cell, the nucleus also directs the metabolic activity of the cell and helps shape the cell into its final form. Instructions for the synthesis of key proteins continuously pass from the nucleus to the cytoplasm, particularly through the channels of the endoplasmic reticulum. Even the basic material of the

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-1266644834078459112011-03-19T19:27:00.000-07:002011-03-19T19:28:43.497-07:00

Tissues are groups of similar cells that carry out a particular activity. Animal tissues each show a marked distinctiveness; however, boundaries between tissue types in plants tend to blur, and one type may change to another in the course of development. Also, structural features, so distinct in animal cells, are very indefinite among plant cells.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-80171979375090397952011-03-19T19:25:00.000-07:002011-03-19T19:27:09.234-07:00

Muscle, nerve, and epithelial tissue are all characterized by the properties of the cells they contain. The various types of muscle tissue show contractility because of the contractile properties of skeletal, smooth, and cardiac muscle tissue cells. The lining properties afforded by the various types of epithelial tissue are likewise derived from the closely apposed and densely packed layer of

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-49769500114772696242011-03-19T19:24:00.000-07:002011-03-19T19:25:13.854-07:00

The organ level of organization is much less definite in plants than it is in animals. At most, we might distinguish roots, stems, leaves, and reproductive structures. Clear-cut functions, the distinguishing features of organs, can be assigned to each of these structures. Roots are involved in anchoring the plant and procuring water and minerals. The shoot or stem supports the entire plant, while

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-54980334590176666862011-03-19T19:22:00.000-07:002011-03-19T19:23:45.286-07:00

The cell must exchange materials with the environment across the surface membrane. An increase in size will result in a relatively greater increase in volume and mass than in surface area, so that the cell will lose effective exchange capacity. This will impose restrictions on the amount of food and oxygen that can move across the membrane to service the metabolic needs of the increased living

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-36779237012053491562011-03-19T19:19:00.000-07:002011-03-19T19:20:18.929-07:00

Lysosomes have been well known since they were described by Christian de Duve in the early 1950s. They are small, usually oval organelles that contain powerful digestive enzymes in an acidic environment. The membrane surrounding the organelle is single and functions to maintain a high degree of internal acidity. The potentially destructive enzymes of the lysosome are probably synthesized by

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-50071044776437488192011-03-19T19:15:00.000-07:002011-03-19T19:17:44.567-07:00

No, in many cells the plasma membrane is encased within an extraneous coat of nonliving material that usually confers some rigidity on the cell it surrounds. Although not affecting permeability, this rigid coat affords considerable protection to the underlying cell, especially in dilute solutions in which the cell might take in water and tend to swell. The coat is known as a cell wall in plant

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-49746532194791726462011-03-19T19:13:00.000-07:002011-03-19T19:14:20.010-07:00

By the late 1960s, evidence was accumulating that the unit membrane hypothesis was inadequate to account for the dynamic nature of membrane proteins, although it was clearly in harmony with the known distribution of membrane lipids. In 1972, a new hypothesis of membrane structure was developed by Singer and Nicholson. Known as the fluid mosaic model, it views the membrane as a double layer of

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-76643134887595457572011-03-19T19:10:00.000-07:002011-03-19T19:12:05.734-07:00

The unit membrane hypothesis of J. D. Robertson was based on electron micrographs taken of red blood cells and the outer myelin sheath that usually surrounds the nerve fibers of all vertebrates. This sheath is derived from the winding growth of Schwann cells around the axon. These micrographs suggested that the membrane possessed a trilaminar (three-layer) structure, in which two

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-43553011288069544632011-03-19T19:07:00.000-07:002011-03-19T19:09:49.464-07:00

The structural components of the cell are best seen with a microscope. Early microscopes utilized light that passed through extremely thin sections of cellular material. These sections were first fixed with substances such as formaldehyde that stabilized the components of the cell. Appropriate strains were then applied that could render visible specific organelles. The cells were, however, killed

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-32285521160991602622011-03-19T18:55:00.000-07:002011-03-19T19:03:56.318-07:00

Robert Hooke was the first scientist to describe cellular structure. He studied thin sections of cork and noted its boxlike structure in a paper published in 1665. The honeycomb arrangement of these box units reminded him of the tiny rooms of a monastery, which are called cellulae in Latin.Hooke could not have seen what were actually the nonliving cell walls of his cork preparation were it not

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-20249452154418842102011-02-21T11:42:00.001-08:002011-03-19T17:24:32.561-07:00

Yes, cells can sun'ive in complete darkness. Anew theory on the origin of life argues that living systems arose in small compartments of total darkness located within iron sulfide rocks that were formed by hot springs on the sea floor. Cells of plant roots live in total darkness and carry out all normal plant cell activities, with the exclusion of photosynthesis. And. if you think about it, cells

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-62304357437656168222011-02-21T11:38:00.001-08:002011-02-21T11:38:54.283-08:00

Cells come in a variety of sizes and shapes. Bacteria are among the smallest (0.2--0.3 j.1m indiameter), while cells of plants and animals are generally larger (10-50 f.lrn in diameter).Cellular size is determined by the surfacelvolume ratio required to maintain access to thesubstances and enzymes that cells need to complete their functions. For further understandingof the surfaceNolume ratio,

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-65789102303767228962011-02-21T11:34:00.001-08:002011-02-21T11:34:47.897-08:00

Most living organisms are aerobic; that is. they require oxygen to complete the total breakdown of glucose. As many as 36 ATP are produced through aerobic metabolism of one glucose molecule. Without oxygen. cells do not synthesize enough ATP to maintain a multicellular organism. ,.105t people think that we need oxygen to breathe. but actually we need oxygen to recycle the spent electrons and

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-82433310530107364782011-02-21T11:31:00.000-08:002011-02-21T11:32:19.932-08:00

We are all aqueous creatures. whether because of living in a watery environment or because of the significant amount of water contained within living organisms. Therefore. all chemical reactions in living organisms take place in an aqueous environment. Water is important to all living organisms due to its unique molecular structure. which is v-shaped, with hydrogen atoms at the points of the vand

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-32495302043539366712011-02-21T09:18:00.000-08:002011-02-21T09:19:51.035-08:00

Another mechanism that explains how the genome can encode for such a wide array of proteins is alterative splicing. Normally RNA splicing removes the introns and then reattaches the exons in sequence. However, in alternative splicing some of the exons may not be reattached. Since the exons contain coding information for the polypeptide, the removal of some of the exons will produce a slightly

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-30602775595093404762011-02-21T09:04:00.000-08:002011-02-21T09:13:10.871-08:00

There were three major theories on the basis of inheritance that existed prior to Mendel. Each of these periodically gained and lost popularity over time, but remnants of each existed well into the nineteenth century. These included: Pangenesis: Pangenesis is the belief that each part of the body contributed a miniature version of itself to the offspring. For example, each finger would contribute

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-69085567673739336302011-01-04T08:53:00.001-08:002011-01-04T08:53:59.499-08:00

The pigment in hair, as well as in the skin, is called melanin. There are two types of melanin: eumelanin, which is dark brown or black, and pheomelanin, which is reddish yellow. Both are made by a type of cell called a melanocyte that resides in the hair bulb and along the bottom of the outer layer of skin, or epidermis. The melanocytes pass this pigment to adjoining epidermal cells called

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-61933680774592533042011-01-04T08:52:00.000-08:002011-01-04T08:53:17.690-08:00

"Numerous insects, such as common houseflies, as well as certain amphibians and reptiles (tree frogs and geckos, for example), are able to walk on and cling to seemingly smooth surfaces--including glass doors and windows."This trick is accomplished not by suction cups or adhesives but rather by a large number of tiny bristles or hairs on the bottom surface of the animals' feet. Scientists have

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-4081866662276333862010-12-19T22:25:00.000-08:002010-12-19T22:32:49.972-08:00

In 1981, the first cases of a new disease now called acquired immune deficiency syndrome (AIDS) were recognized. The victims died of rare infections because their immune systems were crippled. The cause was identified two years later by Luc Montagnier and coworkers. AIDS is produced by human immunodeficiency virus (HIV), of which two major classes are known: HIV-1 and the much less common HIV-2.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-31358081868613098102010-12-19T22:15:00.000-08:002010-12-19T22:21:22.538-08:00

Organisms, from human beings to bacteria, move to adapt to changes in their environments, navigating toward food and away from danger. Cells, themselves, are not static but are bustling assemblies of moving proteins, nucleic acids, and organelles. In fact, many of the proteins that play key roles in converting chemical energy in the form of ATP into kinetic energy, the energy of motion, are

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-31663338179862720372010-12-01T09:05:00.000-08:002010-12-01T09:12:02.965-08:00

It is possible to combine various separation and detection procedures for identification and analysis of Ags and for evaluating the expression of molecules by single cells. Immunoblotting can also be used to assay for the presence of molecules in a mixture as described for the sandwich ELISA. This has now been extended for analysis of products of single cells. For example, to assay for

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-85474670406318598212010-12-01T09:00:00.000-08:002010-12-01T09:04:51.423-08:00

Biostatisticians are statisticians who work in health-related fields. They design research studies and collect and analyze data on problems — such as how a disease progresses, how safe a new treatment or medication is, or the impact of certain risk factors associated with medical conditions. They may also design and analyze studies to determine health care costs and health care quality. They are

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-37315877963690996072010-11-28T05:35:00.000-08:002010-11-28T05:48:02.358-08:00

Crying is a more complicated process than one would at first imagine. First of all, there are really three different types of tears. Basal tears keep our eyes lubricated constantly. Reflex tears are produced when our eyes get irritated, like with onions or when something gets into our eyes. The third kind of tear is produced when the body reacts emotionally to something. Each type of tear

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-75625229930365610172010-11-25T23:28:00.000-08:002010-11-25T23:37:43.409-08:00

No one knows why we yawn. There are lots of theories, some talk about it signalling tiredness or getting oxygen to the brain, others mention clearing out stale air from the lungs and reducing blood carbon dioxide levels. It’s widely assumed that yawning occurs because we are tired or bored or because we see someone else doing it, but there isn’t any hard evidence to support these beliefs.

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-81391791674445526442010-11-25T00:44:00.000-08:002010-11-25T00:47:24.518-08:00

Geneticists use the term mutation rate to indicate the probability that a given nucleotide will be changed by a spontaneous mutation. Mutation rates are expressed as the chance of a mutation per round of replication, per gamete (in eukaryotes), or per cell division (in prokaryotes). Mutation rates also vary considerably between organisms. Bacteria and viruses tend to have higher mutation rates

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-16631778257090548042010-11-25T00:33:00.000-08:002010-11-25T00:41:28.735-08:00

One of the newest additions in the arsenal of molecular biology techniques is the use of DNA microarrays, also known as gene chips or DNA chips. One of the main uses of a DNA microarrays is to study patterns of gene expression. Developed in the 1990s, DNA microarrays have provided a more rapid method of screening genomes for genes that are expressed under specific environmental conditions. The

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-31965966924993707152010-11-25T00:22:00.000-08:002010-11-25T00:27:49.018-08:00

There were three major theories on the basis of inheritance that existed prior to Mendel. Each of these periodically gained and lost popularity over time, but remnants of each existed well into the nineteenth century. These included: Pangenesis - Pangenesis is the belief that each part of the body contributed a miniature version of itself to the offspring. For example, each fingerwould contribute

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-28001634172084474832010-11-23T09:53:00.000-08:002010-11-23T09:58:27.503-08:00

Genomics is the study of genes, their structure and function. In 1990, the U.S. Department ofEnergy and the National Institutes of Health began the Human Genome Project. The goals of thisproject were to determine the sequences of the 3 billion nitrogen base pairs in DNA, to identifythe 30,000 genes in human DNA and to store this information in a database that would be available to researchers. In

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-74877936065170820832010-11-23T09:37:00.000-08:002010-11-23T09:41:12.851-08:00

In the normal process of meiosis, chromosomes pair at the metaphase plate and subsequently separate and migrate to opposite poles. When nondisjunction occurs, the chromosomes do not properly separate. Instead, both members of one homologous chromosome pair migrate to the same pole. As a result, half the gametes will have an extra chromosome, and half will be missing a chromosome. Gametes with

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-69131565132562678322010-11-23T09:27:00.000-08:002010-11-23T09:32:51.580-08:00

There are two important factors that limit the size of a cell and motivate its division. The first is the relative size of the surface area of the plasma membrane and the volume of the cell. When a cell grows, the volume of a cell increases faster than the surface area enclosing it. This is because volume increases by the cube of the radius (volume of a sphere = (4⁄3)πr3, where r is the radius),

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-14733844909031695912010-11-23T09:20:00.000-08:002010-11-23T09:23:08.023-08:00

Another “add-on” feature to C3 photosynthesis is crassulacean acid metabolism (CAM).The physiology of this pathway is almost identical to C4 photosynthesis, with the changes that follow:1. PEP carboxylase still fixes CO2 to OAA, as in C4. Instead of malate, however, OAA is converted to malic acid. (This is a minor difference, since malate is merely the ionized form of malic acid). 2. Malic acid

Kumarnoreply@blogger.comtag:blogger.com,1999:blog-5142461511979121342.post-5307327282509228192010-11-15T08:54:00.000-08:002010-11-15T08:55:50.986-08:00

(a) 264 Gms of CO2 is liberated during complete oxidation of 180 gms of glucose. (b) a-ketoglutaric acid is first dicarboxylic acid formed during Kreb’s cycle. (c) Number of ATP molecules formed by complete oxidation of pyruvic acid is 15. (d) Mercury is used in anaerobic respiration experiments because it does not react with CO2. (e) Rate of respiration is measured by respirometer. (f)

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