Aa × aa,8 患病 / 7 未患病:符合 1:1 杂合患病亲本(Aa,如亨廷顿病)× 未患病配偶(aa)。预期患病比例为 1:1(每胎 50%);15 个子女的期望值为 7.5 患病 / 7.5 未患病。观察值 8/7 的 χ² = 0.0667(df = 1,临界值 3.841)——拟合极好。观察到父传子,证实为常染色体(而非 X 连锁)显性遗传。{"result":"Aa × aa (autosomal dominant): expected ratio 1:1, per-child risk 50%. Observed 8 affected / 7 unaffected: chi-square=0.0667 (df=1) fits the expectation. Male-to-male transmission consistent with AD.","metadata":{"input":{"parent1Status":"affected-heterozygous","parent2Status":"unaffected"},"result":{"expectedRatio":0.5,"perChildRisk":0.5,"chiSquare":0.0667,"significant":false}}}
Aa × Aa,12 患病 / 4 未患病:完美 3:1 两个杂合患病亲本(Aa × Aa,如软骨发育不全——纯合体通常致死)。预期比例 3:1(每胎 75%);16 个子女的期望恰为 12 患病 / 4 未患病。观察值 12/4 的 χ² = 0(完美拟合)。注意许多 AD 疾病的 AA 纯合体病情远更严重(或致死),这是重要的系谱线索。{"result":"Aa × Aa (autosomal dominant): expected ratio 3:1, per-child risk 75%. Observed 12 affected / 4 unaffected: chi-square=0 (df=1) fits the expectation perfectly.","metadata":{"input":{"parent1Status":"affected-heterozygous","parent2Status":"affected-heterozygous"},"result":{"expectedRatio":0.75,"perChildRisk":0.75,"chiSquare":0,"significant":false}}}