BIOB 375 1st Edition Lecture 27Outline of Last Lecture II. Epistasisa. Recessive and dominantb. Duplicate dominantOutline of Current Lecture III. Linkage and Gene Mappinga. Linkage groupb. Genetic distancec. OrientationCurrent LectureLinkage and gene mapping- Linkage group is used to describe the genes that locate on the same chromosome- Since homologous chromosomes have the same gene in the same order, they belong to the same linkage group- How many linkage groups for a man? For a women?o Man = 24, Women = 23- How many linkage groups for a species of AABB, 2n=4X=28?o 14 linkage groups- AAAA, 2n=4X=28?o 7 linkage groups Gene Mapping1. Linkage group2. Genetic distance between genes3. Orientation of genesHow do we know if two genes are linked or unlinked?Ab:aB:ab:AB= 1:1:1:1 Rf= (Recombined/Total) = 0.5If A and B are on the same chromosome, they can arrange in two configurations F1 (AaBb)- Based on the genotype of F1, do we know if this is coupling or repulsion?o No- Based on the genotype of F1, do we know gene A and gene B are linked?o No- SO we need to know the genotypes of the parents- Nonrecombinant gametes (parental gametes)o Ab and ab- Recombinant gameteso AB and ab- Total of the parental genotype gametes are more than the non-parental onesGenetic Distance- Genetic distance is measured by recombination frequency- Rf= (10/100) = 0.1 = 10%- 10% recombination frequency = map distance of 10 map units (cM)A Three-Point Test Cross-
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