ch4 - Ch 4 Determining the Number of Genes for Mutations...

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Ch 4 Determining the Number of Genes for Mutations with the Same Phenotype general genetic approach to studying a biological phenomenon is to isolate mutants which affect that phenomenon complementation test - determines whether 2 independently isolated mutations w/ the same phenotype have affected the same or different genes; aka cis-trans test; developed by Lewis to study Drosophila if 2 mutations affect different genes, then progeny will be wild-type/mutant heterozygous for each of the 2 genes result in wild-type phenotype [aka the 2 mutants complement each other] how many genes are defined by a set of mutations depends on the number of genes involved in the biological process under genetic study ex from Drosophila 2 true-breeding mutants w/ black body crossed all F1 have wild-type yellow body Multiple Alleles – can exist for a given gene multiple alleles constitute a multiple allelic series (Fig 4.3) however, a single diploid individual can only have a max of 2 of these alleles, one on each of 2 homologous chrom carrying the gene locus ABO Blood Group 3 alleles – I A , I B , and i (recessive to other 2) O, A, B, and AB genetic analysis based on blood group can only be used to show that an individual is not the parent of a particular child in blood transfusions, blood types must be matched b/c each blood group allele has specific antigen (molecular that is recognized as foreign by an organism, stimulating production of antibodies; not recognized as foreign by organism expressing them) attached to the outside of the RBC A transfused into A or AB b/c no anti-A antibodies B transfused into B or AB b/c no anti-B antibodies AB transfused into AB b/c O transfused into A, B, AB, or O b/c no A or B antigens AB – universal recipients; O – universal donors relationship between ABO alleles and antigens on RBC most people have H antigen glycolipid on RBC produced by action of dominant H allele at a different locus from ABO locus h/h people = Bombay blood type = anti-O antibodies I A allele produces glycosyltransferase that adds α -N-acetylgalactosamine to the end of the polysacch. A antigen I B allele produces glycosyltransferase that adds galactose to H antigen both I A and I B have some unconverted H antigen I A /I B produce both antigens; homozygous i allele all H antigen Drosophila Eye Color >100 mutant alleles at the white locus, w x – x represents recessive color; ranges between white and wild type brick red experiment
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white f x vermilion m red f eosin f x white m eosin f conclusion: red is dominant to white/eosin; eosin dominant to white number of possible genotypes for n alleles: n(n-1)/2 n homozygous n(n-1)/2 heterozygotes Relating Multiple Alleles to Molecular Genetics
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This note was uploaded on 02/09/2010 for the course BIOL 3301 taught by Professor Hannig/miller during the Spring '10 term at Dallas.

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ch4 - Ch 4 Determining the Number of Genes for Mutations...

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