Cells from a group of Olympic athletes were stained to check for the presence of
ID: 71987 • Letter: C
Question
Cells from a group of Olympic athletes were stained to check for the presence of a Barr body. All of the samples tested positive for a Barr body, however, one of the samples was from a male athlete. What term refers to this observation? Transcriptionally active genes show higher levels of DNA methylation in their promoter regions when compared to transcriptionally inactive genes. There have been numerous reports of males of certain aquatic species showing female traits. This is referred to as feminization. It can be associated with the presence of estrogen-like chemicals in the water. Which mechanism of gene regulation is responsible for the expression of female-specific genes in these males? A nonsense mutation in the CAP gene would result inExplanation / Answer
15. Barr body refers to the inactivated X chromosome. X chromosome inactivation occurs in female somatic cells during embryonic development; randomly one of the X chromosomes is inactivated. If a Barr body is observed in a male, the male must be having the XXY genotype. Inactivation of one of these X chromosomes forms the Barr body.
Such a condition of an extra chromosome than the normal complement is called aneuploidy. Hence, the correct answer is d. Aneuploidy
16. False. DNA methylation is an epigenetic signalling toll that is used to turn off the gene expression.
17. (a) Hormone-receptor complex bidning to a response element
18. cAMP bind to CAP in lac operon, and this binding is required for transcription of the operon. CAP nonsense mutation results in production of a non-functional protein or premature termination of protein synthesis. Absence of functional CAP leads to lack of expression of lac operon
The correct answer is (c) no expression of lac operon
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