Sex chromosome aneuploidy

Other common, but less clinically significant, sex chromosome aneuploidies are the 47,XXX (1/1,000 females) and 47,XYY (1/1,000 males) karyotypes. The former karyotype is associated with increased stature and a mild decrease in IQ, and the latter is associated with increased stature, mild decrease in IQ, acne, and a susceptibility to impulsive behavior (early studies suggesting a propensity to violent criminal behavior have not been substantiated). 

Autosomal trisomy A male with Klinefelter s syndrome Sex chromosome aneuploidy A female with Turner s syndrome Sex chromosome triploidy... 

Aneuploidy in live births and abortions arises from aneuploid gametes during germ cell meiosis. Trisomy or monosomy of large chromosomes leads to early embryonic death. Trisomy of the smaller chromosomes allows survival but is detrimental to the health of an affected person, for example, Down s syndrome (trisomy 21), Patau syndrome (trisomy 13) and Edward s syndrome (trisomy 18). Sex chromosome trisomies (Klinefelter s and XXX syndromes) and the sex chromosome monosomy (XO), known as Turner s syndrome, are also compatible with survival. 

Aneuploidy affecting the sex chromosomes is relatively common and tends to have less severe consequences than does autosomal aneuploidy (although at least one X chromosome must be present for survival). Two aneuploidies of the sex chromosomes are clinically significant. 

Convenient methods378 exist in the mouse for detecting whole-chromosome aneuploidy, as determined by sex-chromosome loss and nondisjunction, ttiese methods are possible because XO female mice and XXY male mice are viable. 

Different species have different numbers of chromosomes, and in Chinese hamsters, an example whose relevance will become clear later on, there are 10 pairs of autosomal chromosomes and one pair of sex chromosomes, making 22 in total. If no mistakes are made during cell division, the counts are preserved after each such division, but this is a highly complicated and still only partially understood process, and mistakes sometimes do occur as a result a daughter cell may contain one or three examples of an autosomal chromosome instead of the expected two. When this occurs in the germ line the result may be an individual with an abnormal number of chromosomes in every ceU, resulting, as noted briefly at the end of Chapter 1, in conditions such as Down syndrome and other trisomies. Errors also occur in somatic ceU division, usually with less-serious results as only a minority of cells are affected. In either case—in individual cells, or in whole organisms—the occurrence of an abnormal number of chromosomes is caUed aneuploidy. 

Carbon tetrachloride was not mutagenic in bacteria. It induced intra-chromosomal and mitotic recombination but not aneuploidy in Saccharomyces cerevisiae, aneuploidy was detected in another single study in Aspergillus nidulans. In vivo, in a single study with Drosophila melanogaster, no sex-linked recessive mutations were observed. 

P-Propiolactone was mutagenic to bacteria. In yeast, it induced mitotic gene conversion, aneuploidy and mutations. It produced heritable translocations and sex-linked recessive lethal mutations in Drosophila melanogaster. In vitro, it induced cell transformation and gene mutations in human cells, and cell transformation, gene mutations, chromosomal aberrations and sister chromatid exchanges in mammalian cells. 

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