supplementary - BIO 390 - GENETICS FROM GENE TO PHENOTYPE...

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BIO 390 - GENETICS FROM GENE TO PHENOTYPE DOMINANCE, EPISTASIS, GENE INTERACTION
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OVERVIEW - Genetic and environmental contributions interact to determine phenotype. - Mutations in same the gene usually result in a mutant phenotype when present together. - Mutations in different genes complement. - Dominance comes in several types. - Most characters are determined by sets of genes that interact with the environment. - Modified genetic ratios reveal gene interactions, including epistasis.
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COMPLEMENTATION TEST - Diagnostic test for allelism - Mutants are crossed to bring two recessive mutations together in heterozygous form • if the phenotype is mutant, mutations are in same gene - they fail to complement - both have loss of function • if the phenotype is wild-type, mutations are in different genes - each mutant contributes normal gene at different locus - complementation due to interaction of different proteins - Heterokaryons used in haploid organisms • two nuclei from different fungal strains occupy one cell
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COMPLEMENTATION TEST - Three phenotypically identical white mutants $, £, ¥ are intercrossed to form heterozygotes • phenotypes reveal whether or not the mutations complement one another - Complementation occurs in the progeny of the cross between £ and ¥ • mutations are in different genes
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COMPLEMENTATION TEST - The progeny of the cross between $ and £ do not show complementation • mutations are in the same gene
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INTERACTIONS BETWEEN ALLELES - Dominant versus recessive • alleles of a single gene can show various degrees of dominance • dominance is determined by type of molecular interaction and level of analysis - Spectrum in dominance/recessiveness relationships of alleles - Complete dominance : phenotypes of heterozygote and homozygous dominant are indistinguishable - Incomplete dominance : heterozygote manifests an intermediate
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This note was uploaded on 07/10/2011 for the course BIO 390 taught by Professor Dr during the Spring '11 term at McMaster University.

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supplementary - BIO 390 - GENETICS FROM GENE TO PHENOTYPE...

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