obtuse wings (obt-) and raisin eyes (rai-) are autosomal recessive mutations on

Question

obtuse wings (obt-) and raisin eyes (rai-) are autosomal recessive mutations on chromosome 3 of Drosophila. A pure breeding obtuse winged female fly was crossed to a pure breeding raisin eyed male to produce wild-type F1. An F1 female was crossed to an obtuse-winged, raisin-eyed male to produce 1000 F2.
a.) Based on the information in figure 5-14, what is the expected phenotypic distribution among the F2? (In figure the figure both genes are on chromosome 3 raisin eye is at 0.2 map units, and obtuse wing is at 77.5 map units)

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Explanation / Answer

1. The given problem is a test cross. 2. In the given problem the two characters are because of recessive genes present on chromosome 3 of Drosophila. 3. When the drosophila with dominant genes (wild type) is crossed with drosophila carrying recessive mutant genes, In the F1 genes we get the wild type drosophila carrying mixture of dominant and recessive genes internally. The F1 externally appears as wild type. 4. An F1 female(genetically carrying wild and recessive genes) was crossed with double recessive (abtuse wing and raisen eye genes) male. 5. When F1 organism is crossed with double recessive organism, we say the cross is test cross. this cross is performed to test whether the F1 is carrying heterozygous genes or not. 6. When we get the test cross ratio 1:1:1:1, we will say that the produced F1 is heterozygous.

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