Chromosome genes

Overproduction of the chromosomal genes for the dihydrofolate reductase (DHFR) and the dihydroptero-ate synthase (DHPS) leads to a decreased susceptibility to trimethoprim and sulfamethoxazol, respectively. This is thought to be the effect of titrating out the antibiotics. However, clinically significant resistance is always associated with amino acid changes within the target enzymes leading to a decreased affinity of the antibiotics. 

Faruqi a.F., Egholm M., Glazer P.M. Peptide nucleic acid-targeted mutagenesis of a chromosomal gene in mouse cells. Proc. Natl Acad. Sci. USA 1998 95 1398-1403. 

Resistance to certain antibiotics can arise as a consequence of mutations to chromosomal genes because of changes in the DNA sequence. Mutations can occin due to single base pair changes. Transitions involve the substitution of one purine (A or G) for another and therefore one pyrimidine (C or T) for another. Transversions involve a change from a pyrimidine to a purine and vice versa. Frameshift mutations occin when one or... 

Taoka, M., Yamauchi, Y., Shinkawa, T., Kaji, H., Motohashi, W., Nakayama, H., Takahashi, N., Isobe, T. (2004). Only a small subset of the horizontally transferred chromosomal genes in Escherichia coli are translated into proteins. Mol. Cell. Proteomics 3, 780-787. 

ALIGNED, HOMOLOGOUS RECOMBINATION swaps information between the same genes on two copies of the same chromosome. Genes are not lost or duplicated, nor is their order changed. Different combination of specific alleles (copies of same gene) does occur. 

Cheng, R. Z., M. A. Shammas, J. Li, and R. J. Shmookler Reis. 1997. Expression of SV40 large T antigen stimulates reversion of a chromosomal gene duplication in human cells. Exp Cell Res 234(2) 300-12. 

Because males have only one X chromosome, gene frequency estimation for X-Hnked traits differs from that of autosomal traits. Consider hemophilia A (Chapter 1), which is an X-linked recessive disease. If a male s X chromosome has a factor VIII mutation, he will have hemophilia A. If his X chromosome does not have the mutation, he will not develop the disease. Thus, the gene frequency for hemophilia A is obtained simply by counting the proportion of affected males in the population (i.e., the proportion of X chromosomes containing the mutation). Approximately one in 10,000 males has hemophilia A. Thus, the gene frequency for this disease, q, is 1/10,000. 

Rice, J.D., Nishioka, K., Sarma, K., Steward, R., Reinberg, D., and Allis, C.D. (2002) Mitotic-specific methylation of histone H4 Lys 20 follows increased PR-Set7 expression and its localization to mitotic chromosomes. Genes Dev. 16, 2225-2230. 

Methylation of certain bases within DNA molecules plays a major role in gene expression, as is evidenced by the transcriptional silencing of X chromosome genes through methylation. The following are recent reviews on the molecular and physical properties of these enzymes [EC 2.1.1.x]. See also specific methyltransferase... 

Datsenko, K. A., and Wanner, B. L. (2000) One-step inactivation of chromosomal genes in Escherichia coli K12 using PCR. products Proc Natl Acad Sci USA. 97, 6640-6645. 

Systematic functional analysis and mapping of X-chromosomal genes in Drosophila melanogaster H. Jackie, MPI for Biophysical Chemistry, Gottingen ... 

The ability of Pseudomonas putida to grow onoctanol is due to two alkane-inducible enzymes - a hydroxylase (this strain also contains a chromosomal gene coding for a hydroxylase) and a dehydrogenase, located on a CAM plasmid (Chakrabarty et al., 1973). 

Furukawa, K., Hayase, N., Taira, K. Tomizuka, N. (1989). Molecular relationship of chromosomal genes encoding biphenyl/polychlorinated biphenyl catabolism some soil bacteria possess a highly conserved bph operon. Journal of Bacteriology, 171, 5467-72. 

Not all hereditary traits follow the Mendelian patterns expected for chromosomal genes. Some are inherited directly from the maternal cell because their genes are carried in the cytoplasm rather than the nucleus. There are three known locations for cytoplasmic genes the mitochondria, the chloroplasts, and certain other membrane-associated sites.285 286 An example of the last is found in "killer" strains of yeast. Cells with the killer trait release a toxin that kills sensitive cells but are themselves immune. The genes are carried in double-stranded RNA rather than DNA, but are otherwise somewhat analogous to the colicin factors of enteric bacteria (Box 8-D). Similar particles (kfactors) are found in Paramecium.287... 

In female mammalian cells most of the genes on one of the two X-chromosomes are completely inactivated. DNA methylation plays a major role in this process.244 245 A perfect correlation has been observed between 5 -methylation of cytosines in CpG islands and inactivation of X-chromosome genes.246 Methylation may also play a role in recombination and repair.247 Methylation of DNA decreases with increasing age.248 It increases as a result of oncogenic transformation of cells.249 Some other modifications of DNA largely limited to bacteriophages are discussed on p. 234 247/250... 

Ribot, E. M., 1998, Rapid amplification oftransposon ends for the isolation, cloning and sequencing of transposon-disrupted chromosomal genes, BioTechniques 24 16-20. 

Miyamoto K, Kesterson RA, Yamamoto H, Taketani Y, Nishiwaki E, Tatsumi S, Inoue Y, Morita K, Takeda E, Pike IW. Structural organization of the human vitamin D receptor chromosomal gene and its promoter. Mol Endocrinol 1997 11(8) 1165-1179. 

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