Males and females often express the same amount of X-chromosome genes despite th

Question

Males and females often express the same amount of X-chromosome genes despite the fact that females have more X chromosomes. Animals approach this problem in different ways. Which of the following is an example? A) Female humans inactivate one of their X chromosomes. B) Male fruit flies double the expression of their X-chromosome genes. C) Some animals, such as birds and the duck-billed platypus, do not have a dosage compensation mechanism. D) All of the above. E) None of the above. How many Barr bodies are present in an individual with Klinefelter syndrome(XXYY)? A) 0 B) 1 C) 3 D) 2 You are examining the chromosomes of a male individual (human) who has a substantial segment of DNA missing from the secondary pseudoautosomal region of his Y chromosome. This would affect A) synapsis. B) the centromere. C) the quantity of genes present on the individual's Y chromosome versus the norm. D) both a and b. E) both a and c. Severity of symptoms of cystic fibrosis may vary from one patient to the next. This variation seen is representative of A) variable expressivity. B) incomplete penetrance. C) codominance. D) dominant alleles. The difference between dominance and epistasis is that A) dominance masks genes at different loci. B) epistasis masks genes at the same loci. C) epistasis masks genes at different loci. D) There is no difference. Assume that you are looking at a case of lethal alleles. Crossing two results in 2/3 green progeny and 1/3 white progeny. If you crossed two green other, how many of the progeny would you predict to be green

Explanation / Answer

34. B) 1 (Explanation - The number of Barr bodies is counted as 1 less than the total number of X chromosomes.)

36. A) Variable expressivity

37. A) Dominance masks genes at different loci (Explanation - In a single gene with multiple alleles, the dominant one masks the recessive one while epistasis is considered as the relationship between genes.)

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