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对双亲正常但有常染色体显性遗传病的患儿做遗传咨询是困难的。如此病为完全外显,它的出现通常归因于基因新突变,复发风险很低。常染色体显性遗传病有不完全外显的个别病例不能总是归于新突变,这一类情形有相当的复发风险,可在无症状双亲以后的妊娠中发现。本文推导一计算复发风险的公式并探讨其意义。复发风险估计的推导:Haldane(1949)曾指出过突变-选择平衡的常染色体显性遗传病的公式:
Genetic counseling is difficult for children with normal parents but autosomal dominant genetic disease. The disease is completely explicit, its appearance is usually due to new mutations in the gene, and the risk of recurrence is low. Individual cases with an incomplete autosomal dominant genetic disease can not always be attributed to new mutations. This type of situation has a considerable risk of recurrence and can be found in pregnancies after asymptomatic parents. This article derives a formula to calculate recurrence risk and discusses its significance. Derivation of Estimation of Recurrence Risk: Haldane (1949) pointed out the mutation - the formula for choosing a balanced autosomal dominant disease: