本题目来源于试卷: Continuity and Change D.8 Inheritance，类别为 IB生物学
[单选题]
In dandelions (Taraxadwn. 0 0r(becncum offh; :3t 8xg,l ywp6ta om5fcn**4gpihvicinale), the allele for diamond-shaped seeds (D) is dominant over oval-shaped seeds (d) and the allele for long seeds (L) is dominant over short seeds (l).
p gfxn:i*o,th4 m c5g;w6yvh3* tlp a8
In a genetic cross between a dandelion that is heterozygous for both traits and a dandelion that is homozygous recessive for both traits, what would be the expected proportion of long seeds?
A. 2 out of 16
B. 4 out of 16
C. 5 out of 16
D. 8 out of 16
参考答案: D
本题详细解析:
Choices A, B and C are incorrect as when the cross is carried out there is a 50% chance of producing long seeds. In a punnett square, there are 4 possible genotypes; DdLl (diamond oval seeds), Ddll (diamond short seeds), ddLl (oval long seeds) and ddll (oval short seeds), each with a 4 out of 16 probability of being produced. Therefore, there is an 8 out of 16 chance of producing long seeds. Choice D is correct.
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