In fruit flies the allele for red eyes is dominant over the allele for pink eyes
ID: 218434 • Letter: I
Question
In fruit flies the allele for red eyes is dominant over the allele for pink eyes .straight wings are dominant over curled wings .lmagine that a red eyed ,straight winged fly that is heterozygous for both characteristics is mated with a fly with pink eyes and curled wings .Predict is hat offspring will be produced by this cross .If these two genes were on different chromosomes.When a geneticist actually carried out this mating ,the were as follows:49% red eyes and straight wings,49 % pink eyes and curled wings 1% red eyes and curled wings, and 1% pink eyes and straight wings .Does this agree with your prediction..How would you explain these results In fruit flies the allele for red eyes is dominant over the allele for pink eyes .straight wings are dominant over curled wings .lmagine that a red eyed ,straight winged fly that is heterozygous for both characteristics is mated with a fly with pink eyes and curled wings .Predict is hat offspring will be produced by this cross .If these two genes were on different chromosomes.When a geneticist actually carried out this mating ,the were as follows:49% red eyes and straight wings,49 % pink eyes and curled wings 1% red eyes and curled wings, and 1% pink eyes and straight wings .Does this agree with your prediction..How would you explain these resultsExplanation / Answer
Answer:
Red eyes = R ; Pink eyes -r
Straight wings = S ; Curled wings = s
red eyed ,straight wing (Rr Ss) X pink eyes and curled wings (rrss) ---Test cross
If the gene are on different chromosomes, the test cross progeny would be in equal in number.
But given percentage of progeny in the question is not like the above. Hence, it was concluded that the genes controlling two traits present on the same chromosome and are linked.
Recombination frequency = (no. of recombinants / Total progeny) * 100
Hint: Recombinant progeny are always very less in number than the non-recombinants if the genes are linked.
RF = (2/100)100 = 2%
RF(%) = Distance between the gene (mu).
So the two genes are closely linked and they are 2 map units apart.
rs RS RrSs (red eyes, straight wings) -25% Rs Rrss (red eyes, curled wings) -25% rS rrSs (pink eyes, straight wings) v rs rrss (pink eyes, curled wings) -25%