Question

The chiasmata are formed as a result of-
A. Exchange of parts of paired homologous chromosome
B. Exchange of part of unpaired non-homologous chromosome
C. Duplication of parts of paired homologous chromosome
D. Loss of parts of unpaired non-homologous chromosome

Answer 1

Hint: During prophase of meiotic cell division, crossing occurs between chromatids of homologous chromosomes resulting in the exchange of genetic material. The point of contact is known to be chiasmata. It is a structure which is X-shaped and generally occurs at the point of crossing over. Usually, recombination or parental cohesion result in the formation of chiasmata.

Complete answer-
Option A Exchange of parts of paired homologous chromosomes- The point of contact between them is known to be chiasmata, where transfer of genetic materials occurs.
Hence option A is the correct answer.
Option B Exchange of part of unpaired non-homologous chromosome-This process is known as “Translocation”. This is an abnormal condition where a chromosome breaks and attaches to another part of the chromosome.
option B is not the correct answer.
C) Duplication of parts of paired homologous chromosome-Duplication refers to replication, so it cannot be true for chiasmata.
option C is not the correct answer.
D) Loss of parts of unpaired non-homologous chromosomes- Chiasmata has to do nothing about unpaired non-homologous chromosomes.
option D is not the correct answer.

Hence option A is the correct answer.

Note:
As we discussed the chiasmata formation, which is a result of the point of contact between two homologous chromosomes. The exchange of materials is known as chromosomal crossover. The chiasmata point is visible after the synaptonemal complex disassembles. Function of chiasmata- it is important for attachment to the spindle poles of the homologous chromosomes.