本题目来源于试卷: Continuity and Change D.5 Gene Expression，类别为 IB生物学
[单选题]
Ligers are the offsp bcc-b57.d 5zr zvrb+;pp. vlxrhsnw kfd56 u2pb:9eku4 o(g 9 xt+1niqing of a male lion and a female tiger. Tigons are the offspring of a female lion and a 9f5wu eht9(ikubdo 4x 2:pn k16n+qsgmale tiger. Ligers tend to be much larger and heavier than their parents, while this is not usually seen with tigons. What is the best explanation for the large size difference between a liger in comparison to the parents?
A. Variation in the epigenetic tags removed from genes prior to zygote formation
B. The Y chromosome suppresses the X chromosome
C. Tigons are always female while ligers are always male
D. The chromosome number is different between female and male lions
参考答案: A
本题详细解析:
Choice A is correct because genes of sperm and ova in tigers and lions undergo varying rates of epigenetic tag removal. Choice B is incorrect. Although in some species sex is partially determined by the Y chromosome suppressing the X chromosome, this is not the reason for ligers being larger than their parents. Choice C is incorrect because both tigons and ligons can be both male and female. Choice D is incorrect because female and male lions have the same number of chromosomes.
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