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Biochemistry

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Purines, Pyrimidines and Nucleic Acid Metabolism

Question
36 out of 59
 

Noble prize recently given for the discovery of (AIIMS Nov 2009)



A RNAi
B Beta transcription factor

C Mitochondrial DNA
D Lipoxins

Ans. A RNAi

a. Two US scientists Andrew Z. Fire at Stanford University in California, and Craig C. Mello at the University of Massachusetts in Worcester on Monday, 02 October 2006 won the Nobel prize for Medicine for their discovery of (RNAi) "RNA interference – gene silencing by double-stranded RNA", in the nematode worm C. elegans which they published in 1998.

b. In 1997, the Fire-Mello team discovered that they were able to "silence" certain genes in a cell's DNA by using two strands of RNA molecules. This prevented the genes from being expressed.

c. Our genome operates by sending instructions for the manufacture of proteins from DNA in the nucleus of the cell to the protein synthesizing machinery in the cytoplasm. These instructions are conveyed by messenger RNA (mRNA).

d. This mechanism, RNA interference, is activated when RNA molecules occur as double-stranded pairs in the cell. Double-stranded RNA activates biochemical machinery which degrades those mRNA molecules that carry a genetic code identical to that of the double-stranded RNA.

e. When such mRNA molecules disappear, the corresponding gene is silenced and no protein of the encoded type is made.

f. Dubbed RNA interference (RNAi), the finding has become an extremely useful research tool, because it allows genetic researchers to "knock-out" specific genes, observe the consequent disruptions, and so determine exactly what the gene does. It is being used as a genome-wide tool, to search thousands of genes in a cell and screen for their function.

g. The technique has already revealed genes responsible for muscle problems and diabetes.

h. A byproduct of the discovery of RNAi was the finding that although cells in the human body only contain one strand of RNA, they do have micro-RNA - tiny sections of RNA that can act a little like double-stranded RNA and also silence the activity of certain genes. Experts believe the body uses micro-RNA in its immune response.

i. In 2004, it was discovered that a mutation in one of these micro-RNAs caused diabetes.

j. Researchers are using RNAi and micro-RNA in drug development, hoping that by shutting down genes that cause disease they will be able to cure diseases such as cancer and HIV.

k. RNA interference occurs in plants, animals, and humans. It is of great importance for the regulation of gene expression, participates in defense against viral infections, and keeps jumping genes under control.

l. RNA interference is already being widely used in basic science as a method to study the function of genes and it may lead to novel therapies in the future.

Purines, Pyrimidines and Nucleic Acid Metabolism Flashcard List

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