"Science and Biotechnology Books Made Simple" |
"Science and Biotechnology Books Made Simple" |
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ScienceDaily
3/29/04 Gene Mutation Involved in Deafness Scientists have discovered an important protein
that is part of the machinery that mediates the sense of hearing. The
protein, cadherin 23, is part of a complex of proteins called “tip
links” that are on hair cells in the inner ear. The tip link is involved
in the conversion of sound waves into electrochemical signals that
communicates with the brain. Mutations in cadherin 23 cause deafness and
Usher Syndrome, which is the leading cause of deaf-blindness. In their Nature article, the Scripps Research
Institute scientist, Mueller and his colleagues have shown that the
protein cadherin 23 is expressed in the hair cell that is part of the tip
link, it has the correct biochemistry and is responsible for opening the
ion channels that are involved in the hearing pathway. The protein also
forms a complex with another protein called myosin 1C, which is involved
in closing the channel. Other studies have shown that when the cadherin 23
gene is deleted in mutant zebrafish, tip links do not form. Interestingly, point mutations in the cadherin 23
protein have already been associated with age-related hearing loss in
mice, and scientists are looking to see if the protein is also affected in
age related hearing impairment. The scientists are trying to identify other molecular components of the tip links. Source-
Nature Online 3/24/04 RNAi used to Screen for Human Cells RNA interference, known as RNAi, is a powerful method of stopping gene activity in lower organisms such as Drosophila and C. elegans. This is done by introducing a long double-stranded RNA molecule into the organism. It has also been shown that RNAi is stopping gene activity in mammalian cells. Scientists from United Kingdom, Netherlands and the United States report the construction of RNAi libraries targeting thousands of human and mouse genes. Large-scale small interfering and short hairpin RNAs (shRNA) screens were then performed on mammalian cells. It was shown that the effectiveness of this technique in a screen for human proteosome defects, as well as the identification of one known and five new components of the p53 (a tumor-suppressor gene) signaling pathway in human cells. Source-
NYTimes
3/3/04 DNA Checks Itself by Using Charged Particles Dr. Jacqueline K. Barton, a professor of chemistry at the California Institute of Technology in Pasadena, CA, is studying the electrical properties of DNA and how it discharges electrons up and down its span to keep itself fit and fiery. She claims that the base pairs are always moving and vibrating, electrons are migrating, holes are opening up and closing through the center of the DNA. DNA, which is the ultimate source of information on how cells should behave, is very stable and very slow to degrade. Dr. Barton and her colleagues are trying to understand how the double helix manages to be at once so twitchy and so reliable and stable for many generations in the course of cell division. The scientists propose that the DNA molecule polices itself electronically, by occasionally delivering a flow of charged particles to check for misplaced bases. If the electrons proceed unhampered, all is well. If there is a problem in the sequence, the flow would short-circuit. This would alert the cell’s DNA repair system to fix the problem. Source-
Yahoo/Biotechnology 2/9/04 Students Discover Genetic Link Students at San Jose's Piedmont Hills High School discovered that they are linked in their DNA to the same ancestor of more than 100,000 years ago in central China or Taiwan. The students tested their own DNA using PCR and gel electrophoresis. They used a specific marker, known as Alu. Alu does not code for any gene or trait. It presence in populations today allows scientists to determine that it first occurred in eastern China or Taiwan. The majority of the students at Piedmont Hills High School are of Asian heritage. A Junior at the school whose family comes from northern India was startled to find out that his DNA was more in common with another classmate of Mexican/European descent than with another northern Indian classmate. Modern humans have a homology over 99% of their genome. Students are wondering whether race does really exist. Source-
Nature 22 January 2004 1/23/04 A Primitive Sex Chromosome Numerous diverse systems for sex determination have evolved in both plants and animals. One system, seen in many animals but a few plants, involves physically distinct sex chromosomes that differ in one sex but are the same in the other. A primitive sex chromosome has now been identified in the papaya plant with a male-specific region that accounts for only about 10% of the chromosome which has undergone recombination suppression and DNA sequence degeneration. The results show that sex chromosomes can evolve from 'regular' chromosomes containing a sex determination gene. Source-
Yahoo/HealthDay 1/22/04 A Bad Gene was once Good Scientists at Stanford University found some tumors activate wound-healing genes which make the tumors spread. The findings could help new ways to treat cancer and those that need more aggressive treatment. According to Dr. Howard Chang, prostate and liver cancers always activated wound-healing genes, however, there were mixed responses in colon and breast cancers. These tumors were highly aggressive and more likely to spread to other tissues.
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SienceDaily.com 1/2/04 A Gene Involved in Rewinding the Developmental Clock of Cortical Nerve Cells Scientists at New York University have identified a gene, Foxg1, in the cerebral cortex that controls the developmental clock of embryonic nerve cells. By eliminating Foxg1 in cortical cells in mice, scientists were able to rewind the clock. According to Dr. Gordon Fishell, this discovery could lead to new methods in replacement therapy by allowing adult stem cells to give rise to wide variety of cells made during normal brain development . The cortex is made up of six layers of cortical cells that are laid down during development at precise time and sequence. The first cortical cells to be born populate layer 1, the most superficial layer, which is made up of Cajal-Retzius (CR) cells. The next cells born migrate to the innermost layer, layer 6. Layers 5, 4, 3, and 2 (in that order) are then formed. Each layer has a specific type of neuron associated with it. Using embryonic mice, the scientists in the study looked at the cortical layers at a time in their development when layers 1, 6, and 5 would normally have already been formed. In mice lacking Foxg1gene, only layer 1, which is made up of CR cells, was present. In later experiments, the researchers temporarily turned off the Foxg1 gene in late progenitor cells, after the normal birth date of CR cells had passed. Cortical cells destined to become layer 5 became CR cells instead. These experiments demonstrated that the gene Foxg1 orchestrates the program responsible for precise sequence of cerebral cortical layers during development. The finding could open a new door to tissue replacement therapy in the central nervous system. __________________________________________________ Send mail to
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