本题目来源于试卷: Continuity and Change D.8 Inheritance，类别为 IB生物学
[单选题]
Which of these statements about genetic disorders is/*yei:. nmz du2 cc :gq,w8gjf(are coy y;h4-5x n3foga pxiu:z 9vs1.v fs-irrect?
I. The majority of genetic disorders are caused by recessive alleles.
II. Genetic disorders can be sex-linked.
III. Offspring of two parents with the same genetic disease will always be affected.
A. All three
B. II only
C. I and III
D. I and II
参考答案: D
本题详细解析:
Choice D is correct because statements I and II are both correct for genetic disorders. Dominant alleles cause some genetic disorders, but most are caused by recessive ones (statement I) and some genetic disorders, such as haemophilia, are sex-linked (statement II). If a parent has a genetic disorder that is caused by a dominant allele, they may be heterozygous, so two heterozygous individuals can have a child that is homozygous dominant for the characteristic and they will not have the disease, therefore statement III is incorrect.
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