这篇博客通过2014年AP生物考试的一个真题，讲解了如何分析家谱图并运用孟德尔定律计算遗传病的概率。重点在于识别性连锁遗传疾病（因所有受影响的个体都是男性）和判断其为隐性遗传（由于父母未受影响但子代中出现病症）。解题过程包括确定疾病基因型、绘制配子组合矩阵以及计算儿子患病的可能性。
(题目选自2014年AP生物真题; MC24)
文字版解析如下：
答案：B
考点：
1. Pedigree Analysis
2. Applying Punnett Squares to Calculate Probabilities
解题思路：
1. Determine the genotype of the affected male in the third generation
2. Use a Punnett Square and cross the affected male with a carrier female
3. Calculate probability of son being affected with the disorder
解题步骤：
- Determine if the disorder is autosomal or sex-linked
o There is a disproportionate number of affected males vs. females. All of the individuals with the disorder (shaded symbols) are males. There are no affected females. This indicates a sex-linked disorder.
- Determine if the disorder is dominant or recessive
o The parents in generation I do not have the disorder, but 2 of their sons in generation II have the disorder. When affected individuals have unaffected parents, it indicates a recessive disorder.
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