Genes acid, Mutations

Peripheral variety is the product of primordial repetitive and reiterative polymerization of nucleic acids, i.e., a contiguous process Variety is the product of biological phenomena, i.e., gene duplication, mutation and selection, and reproductive isolation, i.e. a non-contieuous process. 

These investigations also showed that the conversion of ECB to ECB nucleus would proceed more rapidly if ECB were first solubilized in a suitable solvent such as methanol or acetone. However, if the concentration of solvent was too high, the enzyme activity was reduced. Ideally, the enzyme itself could be tailored to suit the industrially preferred conditions (e.g., to make it more resistant to solvent or active at a different pH). One method for achieving this is to use directed evolution [42], whereby genes encoding the enzyme are mutated, screened and then recombined in vitro. Although the contributions of individual amino acid mutations are small, the accumulation of multiple mutations by directed evolution allows significant improvement in the biocatalyst for reactions on substrates or under conditions not already optimized in nature. This approach was used by Arnold and Moore [43] to make a 150-fold improvement in the activity of a -nitrobenzyl esterase in the presence of 15% DMSO. 

Venier P, Montaldi A, Gava C, et al. 1985. Effects of nitrilo acetic acid on the induction of gene and mutations and sister-chromatid exchanges by insoluble chromium compounds. Mutat Res 156 219. 

The tumor suppressor protein p52> provides yet another example of protein misfolding that can lead to pathological effects, in this case cancers (p is for protein and 53 is for its approximate molecular weight of 53,000). The gene for p53 is located on the short arm of chromosome 17 (17p) and codes for a 393-amino-acid phosphoprotein. In many cancers the p53 gene is mutated and the lack of normal p53 protein has been linked to the development of as many as 40% of human cancers. 

Answer E. For antitubercular activity, isoniazid (INH) must first be metabolically activated via a catalase present in mycobacteria. A decrease in expression of the cat G gene that encodes this enzyme is the mechanism of high-level resistance to INH. Low-level resistance occurs via mutations in the inh A gene that codes for an enzyme involved in synthesis of mycolic acids. Mutations in the gene that codes for DNA-dependent RNA polymerase is an important mechanism of resistance to rifampin and related antibiotics. 

In addition to advances in the chemistry of triplex formation, a number of studies have dxwn results in cells consistent with triplex formation in chromosomal DNA (39,44-46). Peptide nucleic acids have been shown to be of particular value for triplex interactions because cf the relatively high affinity of this modification. They have been shovm to inhibit transcription initiation and elongation, to Hock DNA polymerases (47-49), and to inhibit binary of a number of proteins to DNA (50).Dimeric PNAs have been created that are reported to form PNA/DNA/PNA triplexes and these have been shown to induce gene-targeted mutations in streptolysin-o perme-abilized cells (39). 

Ferry, G., Giganti, A., Coge, F., Bertaux, F., Thiam, K., Boutin, J. A. Functional invalidation of the autotaxin gene by a single amino acid mutation in mouse is lethal. FEBS Lett 581 (2007) 3572-3578. 

Point mutations occurring in the boundaries between the exons and infrons may result in the inability of the pre-mRNA to splice properly and are termed splice mutations. These mutations may result in the loss of many amino acids in the gene product sequence or may cause a frameshift, resulting in total loss of functional gene product. Mutations also may occur in introns with the resultant formation of splice sites that also cause the pre-mRNA to splice abnormally. 

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