Continuity and Change D.8 Inheritance (id: 01ff77a3e)

本题目来源于试卷: Continuity and Change D.8 Inheritance，类别为 IB生物学

[单选题]
What best describes the in 65b4p sy0r84qukf2own. 2: tegcia6i (xlq viheritance of tofu ((4s 0j9lsd1rs kuhe condition shown in the pedigree chart below?lusr o (14 (9sdujfk0s

I. Sex-linked trait
II. Dominant trait
III. Recessive trait

A. I and III
B. I only
C. III only
D. I and II


参考答案:  C


本题详细解析:
Choice C is correct because it is an autosomal recessive trait. We know it is a recessive trait (Statement III) because the unaffected biological parents (individuals 5 and 6) have affected offspring (individual 8). That means both biological parents are carriers of the recessive allele. It is not caused by a dominant allele (statement II) because an affected child (individual 8) has unaffected biological parents. It is not a sex-linked trait (statement III) because an unaffected biological mother (individual 6) and unaffected biological father (individual 5) have an affected daughter (individual 8). If this was a sex-linked condition, in order for her to be affected, she would have received the trait on both copies of the X chromosomes she inherited from her biological parents (if recessive sex-linked) or at least from one biological parent (if dominant sex-linked, but then at least one of the biological parents should have had the condition).

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