In the fruit fly Drosophila melanogaster, the recessive allele (p), when homozygous, determines pink eyes. Pp or PP results in wild-type eye color. Another gene, on another chromosome, has a recessive allele, (sw), which produces short wings when homozygous. Consider a cross between females of the genotype PPSwSw and males of genotype ppswsw. Describe the phenotypes and genotypes of the F1 generation and of the F2 generation.

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Answer:

F1 Generation

Genotype of all offspring PpSwsw

Phenotype of all offspring wild type eye color and long wings

F2 Generation

PPSwSw  - 1, wild-type eye color & &  long wings

PPSwsw- 2, wild-type eye color &  long wings

PpSwSw- 2, wild-type eye color &  long wings

PpSwsw – 4, wild-type eye color &  long wings

PPswsw – 2, wild-type eye color &  short wings

Ppswsw – 1, wild-type eye color &  short wings

ppSwSw – 1, Pink color &  long wings

ppSwsw – 2, Pink color &  long wings

ppswsw – 1, Pink color & short wings

 

Explanation:

Given

p being recessive allele produce pink eyes and the genotype is pp

While PP and Pp produces wild-type eye color.

sw is recessive and hence swsw produces short wings

Genotype of parents

Mother - PPSwSw

Father- ppswsw

The following offspring will be produced

Mother - PPSwSw

Father- ppswsw

F1 generation cross

PSw        PSw         PSw         PSw

psw PpSwsw PpSwsw PpSwsw PpSwsw

psw PpSwsw PpSwsw PpSwsw PpSwsw

psw PpSwsw PpSwsw PpSwsw PpSwsw

psw PpSwsw PpSwsw PpSwsw PpSwsw

Genotype of all offspring PpSwsw

Phenotype of all offspring wild type eye color and long wings

F2 generation cross

PpSwsw * PpSwsw

Mother - PPSwSw

Father- ppswsw

PSw    Psw         pSw         psw

PSw PPSwSw PPSwsw PpSwSw PpSwsw

Psw PPSwsw PPswsw PpswSw Ppswsw

pSw PpSwSw PpSwsw ppSwSw ppSwsw

psw PpSwsw Ppswsw ppSwsw ppswsw

PPSwSw  - 1, wild-type eye color & &  long wings

PPSwsw- 2, wild-type eye color &  long wings

PpSwSw- 2, wild-type eye color &  long wings

PpSwsw – 4, wild-type eye color &  long wings

PPswsw – 2, wild-type eye color &  short wings

Ppswsw – 1, wild-type eye color &  short wings

ppSwSw – 1, Pink color &  long wings

ppSwsw – 2, Pink color &  long wings

ppswsw – 1, Pink color & short wings