Karyotype Features

Another important feature of the transformed/immortalized cells is their karyotype. While in the early stages of transformation, most of the cells will retain a near diploid karyotype. However, once the cells have gone through a crisis event or are growing well beyond the typical crisis period (— 15—30 subcultures), they are aneuploid with a characteristic distribution of individual chromosomes, that is, there are likely to be multiple copies of specific chromosomes while others are not cytogenetically detectable. 

The cri-dii-chat syndrome, which is the result of a terminal deletion of the short arm of chromosome 5 (karyotype 4 ,XY,del[5p]), is a classic example of a chromosome deletion. The name is derived from the French term "cry of the cat," which denotes the characteristic kittenlike cry of babies with this condition. It is rare, affecting approximately 1 in 50,000 newborns. Characteristic features include mental retardation (average IQ of 35), miaocephaly, and wide-set eyes. Most children born with this condition do not survive to adulthood. 

The answer is e. (Murray, pp 812-828. Scriver, pp 3-45. Sack, pp 57-84. Wilson, pp 123-148.) Aneuploidy involves extra or missing chromosomes that do not arise as increments of the haploid chromosome number n. Polyploidy involves multiples of n, such as triploidy (3n = 69,XXX) or tetraploidy (4n = 92,XXXX). Diploidy (46,XX) and haploidy (23,X) are normal karyotypes in gametes and somatic cells, respectively. A 90,XX karyotype represents tetraploidy with two missing X chromosomes, which has been seen in one patient who had features that resembled those of Turner s syndrome. 

The Ewing family of tumors comprises small round cell neoplasms of bone and soft tissue that are, in part, defined by a particular chromosomal aberration [t(ll 22)] and variants thereof. Over the past 15 years, it has become clear that ES and peripheral PNET are part of the same spectrum of neoplastic proliferations. Besides the karyotypic marker just mentioned, both of those tumor types also show neuroectodermal features in tissue culture and similarities in proto-oncogene expression. As classically defined, ES was distinguished from PNET by an absence of pseudorosettes and the lack of ultrastructurally or immunohistochemically detectable neuroectodermal features. However, this diagnostic separation is now considered to be antiquated and has been abandoned. 

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). 

In 1991, five years after the accident, a female root vole (Microtus oeconomus) with an abnormal karyotype (reciprocal translocation) was found within the 30-km radius of the Chernobyl nuclear power plant. These chromosomal aberrations were probably inherited and did not affect the viability of vole populations. Population density of Chernobyl rodents in 1988-89 was about twice that predicted from previous cycles, and was attributed, in part, to increasing radioresistance and abundance of their food supplies. In 1994-95, the diversity and abundance of the small mammal population (12 species of rodents) at the most radioactive sites at Chernobyl were the same as reference sites. Rodents from the most radioactive areas did not show gross morphological features other than enlargement of the spleen. There were no gross chromosomal... 

N-16 Puck s media fail to yield the desired karyotypic and cell phenotypic features. 

Hayflick and associates [179] were the first to provide researchers with human diploid cell lines—cells with a fibroblastic appearance and a karyotype identical to that of the original donor. One interesting feature of these diploid human cultures is that they are not indefinite, they cannot be expanded beyond 55-60 subcultures and still live. In contrast, animal diploid cell lines may grow indefinitely, but morphological and karyotypical alterations take place in subcultures. 

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