Cregion 1, band 1). Use proper symbolism to designate III. NUMERICAL CHROMOSOME

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Cregion 1, band 1). Use proper symbolism to designate III. NUMERICAL CHROMOSOME ABERRATIONS the usual number of chromosomes in human somiatic cells is 46, additions or losses of occur in approximately 1 in 300 newborns. Numeric chromosome abnormalities polyploidy) are more commonly found in pregnancy losses, due to the often lethal material, and occur in approximately 50% of all first trimester miscarriages. whole chromosomes imbalance of chromosome s nonvlable, and monosomy X (Tumer syndrome) are the most common aneu- spontaneous abortuses. While most trisomies have been documented in spontane- chromosomes 13, 18, 21, X, and Y (and rarely 9 and 22) are able to ploidies found in ous abortions, those involving survive and often have of abnormalities that noemal. Such a complex enotypic consequences. Some aneuploidies are associated with a complex may include morphological, physiological, and psychological deviations from of symptoms is called a syndrome. Some of the more common and well- consequences. xciated with chromosomal abnormalities are listed in Table 10.1. Refer to your In attempting to symbolize or describe the chromosome complement of an individual, chromosome some complement begins with the tocal number of chromosomes represented in the sample photograph. textbook for a description of the phenotypic effects associated with each of these syndromes number as well as structure must be taken into consideration. Thus, the description of each Conferees at the 1971 conference in Paris agreed that a plus or minus sign should be placed after the to- tal number but before the appropriate symbol to signify added or missing whole chromosomes. A male having an extra chromosome 13 would be symbolized 47,XY + 13 (Figure 10.5). The conferees agreed Variations in Chromosome Number, Barr Bodies, and Corresponding Phenotypes and Syndromes TABLE 10.1 Phenotype or Syndrome No. of Barr Bodies per Nucleus Total No. of Chromosomes Complement 46 Normal female Normal male Male with XY 46 47, 48, 49 45 XxY, XXXY, XXXXY Klinefelter syndrome Female with Turner syndrome Male with XYY karyotype XYY Female with trisomy X Down syndrome Edwards syndrome Patau syndrome 1 if female, 0 if male 1 if female, 0 if male 1 if female; 0 if male XX or XY (trisomy 21) (trisomy 18) (trisomy 13) The reader is refered to general and human genetics textbooks for a full description of the syndromes listed in this table. XX or XY XX or XY 17

Explanation / Answer

1.trisomy 21.....47,xy,+21

2.47,xxy,+x

3.45,x. OR 45,xo. ...the abnormal cells may have only one x (monosomy)or they may be affected by several types of partial monosomy like deletion of the short p arm of one X chromosome (46,x,del(xp)) or presence of an isochromosome with two q arms (46,x,i(Xq))..

4.cri du chat is due to partial selection of the short arm of chromosome number 5 also called 5p monosomy or partial monosomy...or 5p deletion syndrome or 5p-syndrome.

5.trisomy 18(47,xx,+18)

6.trisomy 13 or trisomy D this can occur either because of each cell contains full extra copy of chromosome 13 or because each cell contains an extra partial copy of the chromosome..(47,xy,+13)

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