Question

How can sister chromatids be bi-oriented on the second meiotic spindle?

Answer 1

Sister chromatids:

1. Despite the separation of homologs, cohesiveness between sister-chromatid pairs is maintained at the centromeres throughout the first meiotic division.
2. As a result, sister chromatids remain connected and may be bi-oriented on the second meiotic spindle.
3. As in mitotic anaphase, the loss of centromeric cohesion promotes sister-chromatid segregation and separation in anaphase II.
4. Meiosis is an important source of genetic diversity. When the initial meiotic division occurs, a random collection of homologs is distributed to the daughter nuclei.
5. Thus, in species with multiple chromosomes, haploid gametes can have either of a large number of maternal and paternal homologs.
6. Crossovers between homologs result in the formation of novel combinations of parental genes.