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Posted on 2016-03-11 18:40:00 in Biology by KOBER

6. A Drosophila melanogaster with tan body and red eyes, line A, is crosses with a D. melanogaster with a black body and cinnabar eyes, Line B. Both lines are true breeding. The resulting offspring are all tan bodied with red eyes. One of the F1 females is crossed with a male from line B. The resulting F2 offspring are as follows: 
Tan body, red eyes 44 
Tan body, cinnabar eyes 6 
Black body, red eyes 8
Black body, cinnabar eyes 42 

a) Are the two loci linked? What hypothesis do you implicitly test to find out? Do a chisquare test, cite your value and explain what it means. 
b) If they are linked, how many map units apart are they? 
c) What proportion of the gametes from the Line B males have the allele for black body and cinnabar eyes? What proportion of the gametes from the F1 males have the alleles for black body and cinnabar eyes? 

7. Imagine that, in finches, beak depth is controlled by three genes, each of which has two alleles, a + allele and a – allele. The baseline depth is 6mm. Each + allele adds .5 mm to the depth of the beak, each – allele subtracts .1mm from the depth of the beak. Two finches with genotypes a+ a- b+ b- c+ c- mate. 
a) What is the beak depth, in mm, for each of the parents? 
b) What is the probability that any given offspring from this cross will have a beak depth measuring 9mm or greater?

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