Linked genes

X-chromo.some linked gene. A.s of 1992, more dran 100 di.sea.se-related gene.s had been mapped to thi.s chromo.some. 

Morris, N. (1994), Linking genes, behavior and responsibility legal implications , in M. Frankel and A. Teich (Eds), The Genetic Frontier, American Association for the Advancement of Science, Washington, DC, pp. 155-160. 

Wakelin, D. and Donochie, A.M. (1983) Genetic control of immunity to Trichinella spiralis influence of H-2-linked genes on immunity to the intestinal phase of infection. Immunology 48, 343—350. 

Stevens JL et al. Linking gene expression to mechanisms of toxicity. Toxicol Lett 2000 112-113 479-486. 

Kavaliers, M., Choleris, E., Agmo, A. and Pfaff, D.W. (2004) Olfactory-mediated parasite recognition and avoidance linking genes to behavior. Horm. Behav. 46, 272-283. 

Andrews, RW. and Boyse, E.A. (1978) Mapping of an H-2-linked gene that influences mating preference in mice. Immunogenet. 6, 265-268. 

It has been shown that both MHC- and non-MHC linked genes are involved in the induction of autoimmune abnormalities in the BN rats [200, 201]. 

Recombinant A cell or an individual with a new combination of genes not found together in either parent usually applied to linked genes. [EU]... 

Recombination The formation of new combinations of genes as a result of segregation in crosses between genetically different parents also the rearrangement of linked genes due to crossing-over. [NIH]... 

Linked genes are likely to be inherited together because they are dose together on the same chromosome. Crossovers that occur between two linked loci during meiosis can produce a recombination of alleles. The frequency of recombination gives a measure of the distance between two genes. 

Baek, S.H., Ohgi, K.A., Rose, D.W., Koo, E.H., Glass, C.K., Rosenfeld, M.G. (2002) Exchange of N-CoR corepressor and Tip60 coactivator complexes links gene expression by NF-kappa-B and beta-amyloid precursor protein. Cell, 110, 55-67. 

The mammalian inactive X-chromosomes in females is associated with H3 methylated at Lys-9 but does not have H3 methylated at Lys-4 [165,166]. Deletion of murine Suv39h genes does not affect H3 Lys-9 methylation at the inactive X-chromosome. Thus, different histone methyltransferases are involved in the methylation of H3 Lys-9 in constitutive and facultative heterochromatin [166]. Further, HPl is not associated with the inactive X-chromosome. Methylation of H3 Lys-9 is an early event in X inactivation in mammals [167,168]. The H3 Lys-9 methylation occurs approximately at the same time as H3 Lys-9 hypoacetylation and Lys-4 hypomethylation, and happens before transcriptional inactivation of the X-linked genes. Upstream of the Xist gene, which codes for a strictly nuclear RNA involved in X inactivation, is a constitutive hotspot of H3 methylated at Lys-9. This early event of H3 Lys-9 methylation occurs simultaneously with or immediately following the association of Xist RNA with the X-chromosome. It has been proposed that the hotspot upstream of the Xist gene serves as a nucleation site for the spreading of Xist RNA and methylated Lys-9 H3 [167]. 

The first indication that modification of specific tail residues were linked to chromatin functional states, came from immunostaining of Drosophila polytene chromosomes with antibodies specific for H4 acetylated at defined lysines [13]. As shown in Fig. 2A, H4 acetylated at lysine 16 (H4acK16) was found almost exclusively on the transcriptional hyperactive male X chromosome (Fig. 2). (Genes on the Drosophila male X are transcribed twice as fast as their female counterparts so as to equalize levels of X-linked gene products between XY males and XX females.) In addition, H4 lysine 12 was found to remain acetylated in centric heterochromatin, while lysines 5, 8, and 16 were all under-acetylated [13]. These observations led to the suggestion that the histone N-terminal tails constitute nucleosome surface markers that can be recognized by non-histone proteins in a modification-dependent manner to alter the functional state of chromatin [13]. 

Since males have only one X chromosome, they usually have only a single allele and are thus hemizygous for all X-linked genes. 

X-linked severe combined immune deficiency (X-SCID)— Absence of a functioning immune system inherited with the X chromosome. X-linked refers to inheritance with the X chromosome, one of the chromosomes involved in determining gender. In humans, women have two X chromosomes, and men have an X and a Y chromosome. X-linked genes can only be inherited by a boy from his mother, since his father would have given him his Y chromosome. 

Roelofs, W. L., Glover, T, Tang, X. H. et al. (1987). Sex pheromone production and perception in European corn borer moths is determined by both autosomal and sex-linked genes. Proceedings of the National Academy of Sciences, USA 84 7585-7589. 

Henner, D.J. Yang, M. Ferrari, E. Localization of Bacillus subtilis sacU(-Hy) mutations to two linked genes with similarities to the conserved procaryotic family of two-component signalling systems. J. Bacteriol., 170, 5102-5109 (1988)... 

---