Question

Genes A, B, and C are located on the same chromosome with following order. Linkage map distances among them are 11cM between A and B and 34cM between B and C.

1. When two parental genotypes were ABC/abc and abc/abc and there were 500 offspring, what would be the possible/expected genotypes and their numbers among the offspring? Assume there was no interference.

Answer 1

Given figures:

Total offspring = 500

Map distance between A and B = 11 cM

Map distance between B and C = 34 cM

Parent cross : ABC/abc * abc/abc

gametes of parent1 = ABC, ABc, AbC, Abc, abc, aBc, abC, aBC

gamates of parent 2 = abc

Offsprings : ABC/abc, ABc/abc, AbC/abc, Abc/abc, abc/abc, aBc/abc, abC/abc, aBC/abc

Parental types :

ABC/abc (NCO)

abc/abc (NCO)

Recombinant types :

ABc/abc (SCO between B and C)

AbC/abc (DCO)

Abc/abc (SCO between A and B)

aBc/abc (DCO)

abC/abc (SCO between B an C)

aBC/abc (SCO between A and B)

Expected double cross over (DCO) = 0.11 (recombinat percentage between A and B) * 0.34 (recombinant percentage between B and C)

= 0.11 * 0.34 = 0.0374 = 3.7%

Expected SCO (A-B) = (Map diatance between A and B)- expected DCO = 11 - 3.7 =7.3 %

Expected SCO (B-C) = (map ditance bewteen B anc C) - expected DCO = 34 - 3.7 = 30.3%

Total cross over (Recombinant) = 7.3 + 30.3 + 3.7 = 41.3 %

Parental = 100 - 41.3 = 58.7%

Percentage of genotype ABC/abc = 29.35% (Half of 58.7% parental)

Percentage of genotype abc/abc = 29.35 (Half of 58.7% parental)

Percentage of genotype Abc/abc = 3.65% (Half of 7.3% SCO (A-B))

Percentage of genotype aBC/abc = 3.65% (Half of 7.3 % SCO (A-B)

Percentage of genotype ABc/abc = 15.15% (Half of 30.3% SCO (B-C)

Percentage of genotype abC/abc = 15.15% (Half of 30.3% SCO (B-C)

Percentage of genotype AbC/abc = 1.85% (Half of 3.7% DCO)

Percentage of genotype aBc/abc = 1.85% (Half of 3.7% DCO)

Number of offsprings with genotype ABC/abc = (29.35 * 500) / 100 = 146.75 = 147 (rounded)

Number of offspring with genotype abc/abc = (29.35 * 500) / 100 = 146.75 = 147

Number of offspring with genotype Abc/abc = (3.65 * 500) / 100 = 18.25 = 18

Number of offspring with genotype aBC/abc = (3.65 * 500) / 100 = 18.25 = 18

Number of offspring with genotype ABc/abc = (15.15 * 500) / 100 = 75.75 =76

Number of offspring with genotype abC/abc = ( 15.15 * 500) / 100 = 75.75 = 76

Number of offspring with genotype AbC/abc = (1.85 * 500) / 100 = 9.25 = 9

Number of offspring with genotype aBc/abc = (1.85 * 500) / 100 = 9.25 = 9