HMB265H1 Chapter Notes -Proband, Autosome, Zygosity
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HMB265H1 Full Course Notes
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Pedigree analysis a scrutiny of mating records. Propositus a member of a family who first comes to the attention of a geneticist; usually, their phenotype is exceptional in some way. Investigator traces the history of the phenotype through the history of the family, then draws a family tree (pedigree) To see single-gene inheritance, the patterns in the pedigree have to be interpreted by mendel"s law of equal segregation. Typical 3:1 and 1:1 ratios are not seen in humans, since we usually have few children. 3:1 and 1:1 ratios might be seen when many similar pedigrees are combined. Autosomal recessive disorders are inherited as recessive alleles, so the unaffected phenotype must be the dominant allele; 2 ways to show autosomal recessive inheritance. The disorder generally appears in the progeny of unaffected parents. The affected progeny include both males and females; this will be simple mendelian inheritance of a gene on an autosome, rather than a gene on a sex chromosome.