LS4 Lect_5

LS4 Lect_5 - 1/18/10 Hemophilia X-linked disease 1. 2. 3....

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1/18/10 1 Hemophilia X-linked disease 1. X-linked traits appear more frequently in males. 2. Mutation and trait never pass from father to son. 3. Affected male always passes mutation to daughters, who serve as carriers who pass the trait to 1/2 of their sons. 4. Thus, trait often skips a generation. Lethal Alleles - All biological functions are under the control of genes, some genes are essential for viability. Yellow gene of mice. Y/y x y/y y/y and Y/y in 1:1 ratio Y/y x Y/y 2 yellow : 1 normal (expect 3:1) backcross yellow and they look like heterozygote. Look at pregnant females and Fnd 1/4 embryos are dead. Y is dominant for yellow hair color Y is a recessive lethal (Y/Y individuals die).
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2 PENETRANCE = % with expected phenotype for a given genotype. Examples of 100% penetrance: Mendal ʼ s Peas, ABO Incomplete penetrance (<100%) Retinoblastoma (Autosomal Dominant). Huntington ʼ s Disease. “Woody Guthrie” Disease. Autosomal dominant. Neurological defects with old age (40s to 80s). EXPRESSIVITY = variation in intensity of phenotype for given genotype. phenylketonurea (PKU) - rare recessive allele in humans. PKU
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This note was uploaded on 04/15/2010 for the course LS LS 4 taught by Professor Ribaya during the Winter '07 term at UCLA.

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LS4 Lect_5 - 1/18/10 Hemophilia X-linked disease 1. 2. 3....

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