03-Extensions1-1 - Extensions of Mendelian Genetics alleles...

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Unformatted text preview: Extensions of Mendelian Genetics alleles incomplete dominance codominance and multiple alleles: the human ABO blood groups modified dihybrid ratios epistasis novel phenotypes complementation lethal alleles sex-linked inheritance penetrance and expressivity genetic imprinting quantitative inheritance pedigree analysis These are patterns of inheritance that follow the basic rules of Mendelian inheritance but yield different phenotypic forms and/or proportions. Extensions of Mendelian Genetics Alleles : different forms of a gene ( G and g ) if the individual has two variations of a gene, the two genes are said to be allelic ( Gg ) if the individual has two copies of the same form of a gene, these two genes are non allelic (because they are identical genes) ( GG or gg ) for two genes to be considered alleles they must map to the same locus (same position on homologous chromosomes) Alleles Null allele : a mutant allele with the effect of either the absence of gene product or the absence of gene product function most null alleles behave as recessive in Mendelian inheritance Alleles: nomenclature e + /e + homozygous dominant e + /e heterozygous e/e homozygous recessive ( ebony ) +/+ homozygous dominant +/e heterozygous e/e homozygous recessive ( ebony ) R 1 & R 2 alternative alleles of gene R I A , I B & I O alternative alleles of gene I (blood types) L M & L N alternative alleles of gene L C R & C W alternative alleles of gene C (eye color: red or white) w, w a , w cf , five of the 100+ alleles found at the w bl , w e Drosophila white locus Partial dominance...
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This note was uploaded on 11/13/2009 for the course PCB 3063 taught by Professor Sotero during the Fall '09 term at University of Central Florida.

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03-Extensions1-1 - Extensions of Mendelian Genetics alleles...

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