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In Drosophila, mutant individuals have a black body (due to recessive allele “b”

ID: 176571 • Letter: I

Question

In Drosophila, mutant individuals have a black body (due to recessive allele “b”), and the wild-typehas a gray body. Individuals with the recessive phenotype vestigial (vg) have wings that are crumpled andmuch shorter than wild-type. Calculate the map distance between the two genes if the follow offspringphenotypes and frequencies were obtained in a cross between a double heterozygous female and a doublehomozygous recessive male.
Offspring:    gray normal 283  

Gray vestigial  1294

Black normal  1418  

Black vestigial  241

Explanation / Answer

phenotype

observed

Grey normal

283

recombinant

Grey vestigeal

1294

parental

Black normal

1418

parental

Black vestigeal

241

recombinant

total

3236

Total recombinant =524

% of recombination= (524 /3236) x 100

=16.19%

Hence two genes are 16.2 mu or 16.2 cM apart

phenotype

observed

Grey normal

283

recombinant

Grey vestigeal

1294

parental

Black normal

1418

parental

Black vestigeal

241

recombinant

total

3236

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