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 offsprin . u+r gtf6nv*3wu;kccg of a male lion and a female tige83;gnl x*dh +af:rj eur. Tigons are the offspring of a female lion and a male tiger. Ligers tend to be much larger and heavier than their parents, while this is not gh*rxunf;8+ l3:jaed 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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