Question

Describe the role of chiasmata in chromosome segregation during meiosis.

Answer 1

Explanation:

The phase of Prophase I of meiosis is very long and divided into 5 subphases: Leptotene, Zygote, Pachytene, Diplotene, and Diakinesis. During a phase of the Diplotene, the degree of condensation is high, which allows individualizing the sister- chromatids that remain attached by the cohesins. The synaptonemal complex disintegrates, and from the centromeres begins a repulsion between homologous chromosomes, which remain associated only with the places where they occur as permutations.

These sites are called chiasmas (Greek, crossed) because they show the crossover of homologous chromatids. Chiasmas represent the cytological finding of the occurrence of permutation. The presence of at least one bivalent chiasm is essential to ensure the correct segregation of the homologous chromosomes in anaphase I.