IMED1002 Lecture Notes - Lecture 15: Haemophilia, Consanguinity, Zygosity
12 Jul 2018
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Understand the possible genotypes within pedigree charts; Cf pedigree: assign genotypes to each person in the pedigree, autosomal recessive traits: When heterozygous parents, about a quarter offspring affected. More frequent in children of consanguine marriages. Hu(cid:374)ti(cid:374)gto(cid:374)"s diso(cid:396)de(cid:396) pedig(cid:396)ee: gene on chr 4, recall: tri-nt repeat expansion and poly gln (glutamine) toxic protein, autosomal dominant traits: Affected offspring has affected parent (unless new mutation) Unaffected parents do not transmit the trait. If 1 parent heterozygous 1 unaffected about half offspring affected. Dominant means each affected individual has atleast one affected parent. Usually more males than females affected (males only 1 x chr, no 2nd x chr to counteract effects of recessive allele) Affected sons usually born to unaffected mothers, so skips generations. A(cid:271)out half of hete(cid:396)oz(cid:455)gous (cid:272)a(cid:396)(cid:396)ie(cid:396) (cid:373)othe(cid:396)"s so(cid:374)s affe(cid:272)ted. All daughters of affected fathers are carriers. Rickets pedigree: x-linked dominant: both males and females affected, often more females than males. Does not skip generations, affected males must have affected mother.
