For the following, each numbered data set is for a different situation. Don\'t a

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For the following, each numbered data set is for a different situation. Don't assume that the genes are in the same order. The order of the questions below is how you attack the problem. (After you finish, you should start again, and see how fast you can work; hopefully on the second time, you will see that this is really quite systematic.) Recessive phenotypes are symbolized by lowercase letters. (Phenotypes of progeny are counted after crossing to a tester strain a b c.) Abbr.: Phenotype, Observations, Genotype, Recombinants for a and b and c (Por R) Middle Gene, coinificient of coincidence, interference, total number of recombinants, total number of individuals, Distance between each pair of markers. Map should be short side marker, shortest distance, middle marker, longer distance, long side marker Pheno Obs Geno Ra-b? Ra-c? Rb-c? WT1 Pheno Obs Geno WT 30 Ra-b? Ra-c? Rb-c? 142 a b4 a c a b 3 ac 291 b c abc I Middle_ tot, R Middle tot, R interf:- Dist interf: Dist Ma

Explanation / Answer

Hi

Look at the genes and thier numbers. Always the highest numbered one are parental types: so aBC (77) and Abc(77) are parental.

The lowes ones are Double cross over mutants: WT = ABC (1) and abc(1) are DCOs.

Now, compare the DCO and parental type and look for the difference. The gene A is chaned and rest are all the same. So the gene in middle is gene A.

The gene order is BAC.

Now, the recombination between B and A would result in Bac (31) and bAC(31)

RF between A and B = 31+31 + DCO /total

= 62 + 2 / 226

= 0.2831

= 28 mu gene distance.

simialarly, recombination between A and C would result in BAc (4) and baC (4)

RF between A and C = 4+4 + DCO /total

= 8 + 2 / 226

= 0.044

= 4.4 mu gene distance.

so recombinants are 1+31+4+4+31+1 = 72

total =226

Coefficient of coincidence = observed DCO - expected DCO

expected DCO = 2 x (recombination through A and B ) x )recombination through A and C).

= 2 x (0.28)(0.044)

= 0.024

interference (I) = 1 - COC

I = 1 - 0024

I = 0.976

Map: B---28mu----A--4.4mu---C

distnce B to A = 28 mu

A to C = 4.4 mu

B to C = 32.4 mu

you can try another one , with similar logic. If any issues please get back in comments.

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