biol139-lecture20-2011

5 mu between y and ec does not account for 55 between

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Unformatted text preview: ec+ or y+ ec because no information given for w Males Phenotype F2 y w ec y+ w+ ec+ y+ w ec y w+ ec+ y w ec+ y+ w+ ec y w+ ec y+ w ec+ Observed Numbers 4685 4759 70 80 193 207 y – w (SCO) 70 + 80 + 3 + 3 10,000 w – ec (SCO) 193 + 207 + 3 + 3 10,000 distance between y-ec: (DCO) 70+80+193+207+3+3+3+3 = 0.0562 10,000 0.0562 x100 = 5.62 5.62 3 3 1.56 + 4.06 = 5.62 Three-point crosses Three-point The two largest phenotypic classes represent the parental The largest parental + + + classes (nonrecombinant) y w ec ec y w ec The two smallest phenotypic classes represent The smallest + + + double crossovers double y w ec y w ec The gene whose alleles have been ‘switched’ ‘switched’ between parental and double crossover classes is between parental double in the middle i.e. w i.e. Double crossovers must be accounted for twice when Double twice calculating the distance between the two outside calculating outside genes genes Don’t know order or map distances. Where to start p and j Recombinants = p+j pj+ 52+46+4+2 = 104 500 500 =0.208 = 20.8% = 20.8 m.u r and j Recombinants = r+j rj+ 22+22+4+2= 50 500 500 =0.10 = 10.0% = 10.0 m.u. p j r p and r Recombinants = p+r p r+ 52+46+22+22=142 500 500 =0.284 = 28.4% = 28.4 m.u. 28.4 m.u. 10.0 m.u. 20.8 m.u. Now correct for pr Now pr =52+46+22+22+4+4+2+2 =154 52+46+22+22+4+4+2+2 500 500 500 = 30.8 m.u. 30.8 Like two single cross overs each one accounting for the double cross over. Determining gene order; faster way Determining 1. pick a P genotype = vg b pr 2. pick a DCO genotype = vg b pr+ 3. compare -Two allele pairs will match (will be either the same or different) and the odd one out is the gene in the middle. • Determine pr is in center by comparing parentals with DCO so vg and b are outside genes. • Determine distance of outside genes (vg and b) by adding all recombination events and correct for DCO =252+241+131+118+13+9+13+9/ 4197 = 18.7 m.u. events • Once have accurate map distance for outside genes determine one other pair (i.e vg/pr), then subtract this distance...
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This note was uploaded on 10/04/2011 for the course BIOL 139 taught by Professor Christinedupont during the Spring '10 term at Waterloo.

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