Two Strains of Australian Wombat Were Crossed

question 24

Essay

Two strains of Australian wombat were crossed.Meiotic metaphase configurations of the F₁ hybrids are diagrammed below. In both strains of wombats,n = 4.The black dots are the centromeres,a and b are genetic markers located on chromosome 2,c is located on chromosome 3,and d is located on chromosome 4.
a)How do the chromosomes of the two parental strains differ? Use terminology that most accurately describes each chromosomal rearrangement.
Chromosome 1:
Chromosome 2:
Chromosome 3:
Chromosome 4: b)In the two parental strains,the map distance between the a and b loci is not the same.Explain why.
c)Assume that during meiosis in the F₁ above,a crossover always occurs between the a locus and the centromere of chromosome 2.
(i)What proportion of gametes produced by the F₁ hybrid will be viable? (Note: You must consider the behavior of all 4 chromosomes in answering this question.)
(ii)What will be the genotypes of the viable gametes at the a and b loci?
(iii)What will be the genotypes of the viable gametes at the c and d loci?

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