Question

Terminalization of chiasma occurs during
A. Zygotene
B. Pachytene
C. Diplotene
D. Diakinesis

Answer 1

Hint: Chiasma in genetics is a term used to refer to the point of contact between two non-sister chromatids of homologous chromosomes. This results in crossing over of genetic material. It is responsible for variations. It occurs during the fourth stage of meiosis.

Complete answer: Meiosis is a specialized type of cell division. It involves a reduction in the number of chromosomes in daughter cells than the parent cells. This type of meiosis is evident in sexually reproducing organisms. The gametes which are mediators for sexual reproduction are made by this type of cell division. It consists of various stages and each stage is characterized by a special event occurring in it eventually causing cells to divide. The cell divides twice forming four daughter cells.
The first division is called Meiosis I and it involves stages as Prophase I, metaphase I, anaphase I, telophase I, and cytokinesis I. The prophase I stage of meiosis I is characterized by condensation of chromosomes. The homologous chromosomes come towards each other. This pairing of homologous chromosomes is termed as a synapse. Crossing over takes place during synapse. The process is called synapsis. During synapsis, the two homologous chromosomes that have similar genes placed at similar points cross over. In actuality, the chromatids of these homologous chromosomes form synapses. The non-sister chromatids are those that are situated on the different chromosomes of homologous pairs. So these non-sister chromatids cross over and transfer their genetic segments. The point where transfer happens is called chiasma. The chiasma stage occurs during the diplotene stage of Prophase I. It is the fourth stage after leptotene, zygotene, and pachytene.
So, the correct answer is option C.

Note: The chiasma formation results in the transfer of genetic material between two segments of non-sister chromatids resulting in mutations. The mutation or recombination of the genetic material results in variations. Also, chiasmatic formation prevents aneuploidy. Aneuploidy refers to an abnormal chromosome count in cells.