In crane-fly spermatocytes, the incidence of bivalents exhibiting diamphitely is reported to be at a significantly high level during recovery from cold treatments that arrest meiosis in those cells at prometaphase of the first division.

(a) If you were to find such bivalents in a preparation of spermatocytes, what would you suspect about the spacing of their kinetochores in comparison to what is normally seen on normal bivalents?

(b) If you were to follow a cold-recovering spermatocyte exhibiting diamphitely in one of its bivalents as it progressed from metaphase to anaphase of the first division of meiosis, what would you expect to be the fate of the two homologues (half-bivalents in anaphase) comprising it in comparison to other half-bivalents that appeared to be normally disyntelically oriented?

(c) How might that fate figure into the possibility of nondisjunction?

2. In crane-fly spermatocyte meiosis, anaphase lagging of the X and Y sex chromosomes during the first division of meiosis is a consequence of the orientation of their kinetochores.

(a) Describe that orientation, (b) correctly state the terminology that applies to it, and (c) explain why – as the events of the first division unfold – lagging is observed in X and Y, whereas autosomes segregate to the poles during anaphase A of the first meiotic division.

3. What happens to the each of the bundles of kinetochore microtubules connected to X and Y in crane-fly spermatocytes as X and Y engage in distance segregation during anaphase B of the first division of meiosis?

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1 a If bivalents in cranefly spermatocytes are exhibiting diamphitely it would suggest that the spacing of their kinetochores is abnormal compared to ... View the full answer