BIOL 2300: Exam 3 Quiz Questions with Complete Solutions

BIOL 2300: Exam 3 Quiz Questions with Complete Solutions The most common aneuploidy seen in living humans has to do with ___________. Sex Chromosomes Mammals with multiple X chromosomes undergo random X-inactivation in each nucleus early in gestational development. This results in only one X chromosome being active in each cell, no matter how many X chromosomes are present.Which sex chromosome genotype(s) would you expect not to express Xist RNA? XY A boy with Klinefelter syndrome (47,XXY) is born to a mother who is phenotypically normal and a father who has the X- linked skin condition called anhidrotic ectodermal dysplasia. The mother's skin is completely normal with no signs of the skin abnormality. In contrast, her son has patches of normal skin and patches of abnormal skin. (a) Which parent contributed the abnormal gamete? (b) Using the appropriate genetic terminology, describe the meiotic mistake that occurred. Be sure to indicate in which division the mistake occurred. The father must have contributed the abnormal X-linked gene.; b. Non-disjunction must have occurred during meiosis I. For a species with a diploid number of 12, indicate how many chromosomes will be present in the somatic nuclei of individuals that are (a) haploid, (b) triploid, (c) tetraploid, (d) trisomic, and (e) monosomic. Enter your answers in the appropriate blank as a whole number. A) 6 B) 18 C) 24 D) 13 E) 11 Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. While there is reduced fertility in both sexes, females have higher fertility than males. Van Dyke et al. (1995; Down Syndrome Research and Practice 3(2):6569) summarize data involving children born of Down syndrome individuals. Given the fact that conceptuses with 48 chromosomes (four #21 chromosomes) are not likely to survive early development, what percentage of surviving offspring would be expected to be normal if both parents have Down syndrome? 1/3 Predict how the synaptic configurations of homologous pairs of chromosomes might appear when one member is normal and the other member has sustained a deletion or duplication. There will be point-for-point pairing in all sections that are capable of pairing. The section that has no homolog will loop out to form a deletion or compensation loop. A woman who sought genetic counseling is found to be heterozygous for a chromosomal rearrangement between the second and third chromosomes. Her chromosomes, compared to those in a normal karyotype, are diagrammed below: The women has had two miscarriages. What is the chance that she could have a normal child? The chance of a normal child is approximately one in two; however, half of the normal children will be translocation carriers. When the cloned cat Carbon Copy (CC) was born, she had black patches and white patches, but completely lacked any orange patches. The knowledgeable students of genetics were not surprised at this outcome. The donor nucleus had an orange allele that was inactivated and remained inactivated in CC. The remaining black allele was the only one that could be expressed. What are pseudoautosomal regions on the sex chromosomes? homologous regions of the X and Y chromosomes