Question

Which stage is marked by termination of chiasmata
A. Zygotene
B. Pachytene
C. Diplotene
D. Diakinesis

Answer 1

Hint: All these processes are found in meiosis and it has different stages of cell division now let us find the last stage.

Complete answer:
To solve this question, at first, we have to know the different stages of meiosis prophase 1. The meiosis I contain is of following stages- Prophase, metaphase, anaphase, telophase. The prophase I contains is leptotene, zygotene, pachytene, diplotene, diakinesis. The two homologous chromosomes do not completely separate but it remains attached together at one or more ends as indicated via X arrangements known as Chiasmata. Terminalization of chiasma takes place throughout diplotene,after crossing over at pachytene, and terminalization completion takes region in diakinesis.

Now lets us find the solution from given options –
Zygotene is the sub-stage where synapsis among homologous chromosomes begins. It is also called zygonema. This synapsis can form up and down the chromosomes permitting many points of contact known as 'synaptonemal’ complexes; this could be compared to a zipper structure, because of the coils of chromatin.
In pachytene once the synapse is formed it is known as a bivalent in which a chromatid of one pair is connected to the chromatid in a homologous chromosome and crossing over can occur.
During the diplotene phase the two homologous chromosomes start to migrate apart as the synaptonemal complex disintegrates between the two chromosomal arms and they begin to repel one another. This allows the two chromosomes to move apart, held only by the chiasmata.
Diakinesis is the final step of Prophase 1 and is the termination of the condensing of the chromosomes; this allows the chiasmata and bivalent structure to bevisible more clearly under an electron microscope. The chromosomes are at their most condensed shape throughout diakinesis.

Thus, the right answer is option D. i.e. Diakinesis.

Note: The chromosomes are decondensed during diakinesis phase. In this stage a further condensation of the chromosomes and, simultaneously, a further separation of the chromatids takes place that, however, still hang together at the chiasmata.