Genetics

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1) The F2 progeny from a cross exhibits a modified dihybrid ratio of 9:7 instead of 9:3:3:1. What phenotype ratio would be expected from a testcross of the F1 progeny?

2) In Drosophila, mutants a through g all have a white eye phenotype. The following data shows the results of pairwise combinations in a complementation test:
a b c d e f g
g + - + - + + -
f - + - + + -
e + + + + -
d + - + -
c - + -
b + -
a -

How many genes are present?
Which are defects in the same gene?

3) A male Drosophila fly is found with white eyes. How would you determine if the mutant in this fly is the same as Morgan’s original white fly. Show the cross(es) you would do. You must use proper symbols.

4) What does the term complementation mean? If two different mutations that have the same phenotype complement each other, what can you conclude about those two mutations?

Could you help me with these questions to help me study for my next test?

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