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一般记录、讨论遗传病的出发点是采用一定的遗传模型,然后观察某种疾病在一个家系中的出现方式是符合那一种模型。到目前为止已经确定或推测了所谓正常特征的2,300个以上的基因位点。根据遗传特征的不同,对遗传病可作如下分类:常染色体显性遗传,常染色体隐性遗传、X连锁显性遗传、X连锁隐性遗传,Y连锁遗传。现已知先天性代谢异常症的突变基因大部分为纯合子,因而表现出酶的“缺陷”或“缺少”的隐性遗传病。换句话说,只要在2个等位基因当中有一个是正常基因的杂合子,就能维持正常生理机能而不发病。
General records, the genetic basis for the discussion of genetic disease is the use of a certain genetic model, and then observe a disease in a pedigree appears to be consistent with that model. To date, more than 2,300 gene loci for so-called normal features have been identified or speculated. According to the different genetic characteristics of genetic diseases can be classified as follows: autosomal dominant, autosomal recessive, X-linked dominant inheritance, X-linked recessive inheritance, Y-linked inheritance. It is now known that most of the mutated genes of congenital metabolic disorders are homozygous and thus exhibit “defective” or “missing” recessive genetic disease of the enzyme. In other words, as long as one of the two alleles is a heterozygote for a normal gene, normal physiology can be maintained without disease.