Drosophila eyes are normally red. Several purple-eyed strains have been isolated

Question

Drosophila eyes are normally red. Several purple-eyed strains have been isolated as spontaneous variants (mutants) and the purple phenotype has been shown to be inherited as a Mendelian autosomal recessive in each case. To investigate allelism between these different purple mutations, two purple-eyed strains were crossed. If the purple mutations are in different genes (that is, they are not allelic), the F1 is expected to be

A) all red

B) all purple

C) 34 red, 14 purple

D) 12 red, 12 purple

E) 34 purple, 14 red

Justify your Answer

Explanation / Answer

F1 generation has all purple eyed strains as its mentioned that trait is inherited in autosomal recessive fashion...implying two mutant alleles must be present to express that character..!

so supposing purple eyed strain is expressed by mutant allele p and the normal red eyed as R.

so pp must be needed for purple eyes,,. even if single R is present it leads to red eyed strain...

so as 2 purple eyed strains are crossed... the entire f1 generation wil have the mutant alleles only leading to 4 purple eyed strains as result.

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