Question 3!! 1. Determine the gene order and phase for the genes A, B and C. 2.

Question

Question 3!! 1. Determine the gene order and phase for the genes A, B and C. 2. Determine the distance between genes A, B and C. 3. Draw a linkage map with the correct gene order, allele combinations genes. For this exercise, phenotypes with capital letters are dominant and phenotypes in lower case letters are recessive. For example, "phenotype A" mean the dominant phenotype for the gene and "phenotype a" means the recessive phenotype for that gene. Show all your calculations. Remember that the three genes can be in any order. Remember that the dominant alleles do not necessarily need to all be on the same chromosome in the triple heterozygote parent. Phenotypes N aTB Atb 309 305 51 ATb atB 54 atb ATB AtB aTb Total 843 3 4 56 61

Explanation / Answer

as we know, we get maximum no. of parental type genotype and minimum no. of double crossover type genotype. so aTB=309 & Atb=305 are parental type and atb =3 & ATB = 4 are double cross

comparing these two (parental & double crossover), only A change so gene order will be TaB or BaT

Single crossover products-

t-a recombination frequency= 100*(51+54+3+4)/843 = 13.29

a-b recombination frequency= 100*(56+61+3+4)/843 = 14.70

t-b recombination frequency= 100*(51+56+(2*3)+54+61(2*4))/843 =27.99

so the distance between a & t genes is 13.29 map unit,

distance between a & b genes is 14.70 map unit,

distance between b & t genes is 27.99 map unit

parent 1            T       13.29      a        14.70             B

parent 2           t                      A                             b

                     27.99

TAb 51 taB 54 tAB 56 Tab 61

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