Karyotype change

Figure 9.5 Karyotypic changes during initiation, promotion, and progression stages of carcinogenesis.

Hansteen I-L, Hilt B, Lien JT, et al. 1993. Karyotypic changes in the preclinical and subsequent stages of malignant mesothelioma A case report. Cancer Genet Cytogenet 70(2) 94-98. 

Oshimura M, Hesterberg TW, Barrett JC. 1986. An early, nonrandom karyotypic change in immortal Syrian hamster cell lines transformed by asbestos Trisomy of chromosome 11. Cancer Genet Cytogenet 22 225-237. 

Frost, P., Kerbel, R. S., Hunt, B., Man, S. and Pathak, S. (1987). Selection of metastatic variants with identifiable karyotypic changes from a nonmetastatic murine tumor after treatment with 2 -deoxy-5-azacytidine or hydroxyurea implications for the mechanisms of tumor progression. Cancer Res. 47, 2690-2695. 

Sargent EM, Sattler GL, Roloff B, et al. 1992. Ploidy and specific karyotypic changes during promotion with phenobarbital, 2,5,2, 5 -tetrachlorobiphenyl, and/or 3,4,3, 4-tetrachlorobiphenyl in rat liver. Cancer... 

Next to the lack of the high compositional heterogeneity and lack of CpG islands, other general features distinguish reptilian genomes from those of warm-blooded vertebrates (see Table 12.3). Indeed, T bands are absent in chromosomes from turtles, lizards and snakes (M. Schmid, personal comm.), and karyotypic change and species formation are much slower in this vertebrate class (as they also are in fishes and amphibians) compared to warm-blooded vertebrates (Bush et al., 1977 see also Bernard , 1993b). 

The DNA in tumor cells tends to become increasingly unstable. DNA instability may manifest itself in changes in the appearance of a cell s chromosomes when they condense immediately prior to cell division, or mitosis. The appearance of the complete set of condensed chromosomes at mitosis is called the karyotype. Changes in tumor cells karyotypes may include breaks or rearrangements within chromosomes or the translocation of a piece of one chromosome to another chromosome. DNA instability inaeases the risk of fresh mutations that may further accelerate a tumor s growth. 

Progression This is an irreversible change and involves the continuing evolution of a basically unstable karyotype. Karyotype instability increases as the neoplasm grows. 

Transformation Cell changes manifested by escape from control mechanisms, generally resulting in increased growth potential, alterations in the cell surface, and karyotypic abnormalities. Cell transformation generally occurs as a result of the acquisition of genetic information as by a virus entering the cell. 

The answer is a. (Murray, pp 812-828. Scriver, pp 3-45. Sack, pp 97-158. Wilson, pp 23—39.) Females have two alleles for each locus on the X chromosome because of their 46,XX karyotype. One normal allele is by definition sufficient for normal function in X-linked recessive disorders, so that females with one abnormal allele are carriers instead of affected individuals. Only when the companion normal allele is disrupted or missing does the abnormal allele cause disease. The Lyon hypothesis predicts that X inactivation is early, irreversible, and random, but some females inactivate only the X chromosome carrying the normal allele. X autosome translocations may disrupt an X chromosome locus and cause disease because the translocated autosome must remain active to avert embryonic death nonrandom inactivation of the normal X chromosome thus ablates expression of its normal allele. Females with Turner s syndrome, like males with 46,XY karyotypes, have only one X chromosome and can be affected with X-linked recessive diseases. Conversely, females with triple X or trisomy X syndrome have three alleles at each X chromosome locus and are not affected with X-linked recessive disorders. Since choices c, d, and e each require two genetic changes, they are less common than choice a. 

The epigenome preserves acquired information is this faculty heritable It is the DNA the template of heredity claimed to be identical in all the cells of the multicellular hosts. Is it possible that DNA is a subject of environmentally induced changes Instead of equiceUuIar identity, somatic cell mosaicism (cells of different karyotypes in an individual) introduces changes in the DNA molecules in some... 

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