Question

An organism has 27 chromosomes. Use a * to represent centromeres, and a $ to represent repetitive regions of DNA caused by transposable elements. Chromosome 4 has the sequence A$BC*$DE, while chromosome 17 has the sequence L$MNO$*PQ.

1. If chromosome 17 misaligns with itself (without flipping backward) during meiosis I and undergoes crossing over in the repetitive region, what will be the sequences of chromosome 17 that result in each of the four gametes produced by this cell?

2. What abnormal chromosome sequences could be created if chromosome 4 misaligned with itself (without flipping backward) (there should be 2 of these)?

3. Which of the abnormal sequences would be likely to be left hanging out in the cytoplasm (where it would likely degrade) without being tugged into either nucleus?

4. If instead of misaligning with itself, chromosome 4 aligned with chromosome 17 (without flipping backward or having any double crossover events), provide 6 of these sequences, and label the ones that have too many or too few centromeres?

5. For a Eukaryotic animal cell, is it generally more deleterious to be triploid or to have trisomy of a single chromosome? Why is triploidy an impossible long-term state for the generations that come after a triploid organism that reproduces sexually?

Answer 1