Question

The enzyme recombinase is required at which stage of meiosis?
A) Pachytene
B) Zygotene
C) Diplotene
D) Diakinesis

Answer 1

Hint: The enzyme recombinase helps in recombination of genes between homologous chromosomes. This process is called crossing over. It takes place in the prophase-1 of meiosis.

Complete Answer:
Meiotic division occurs in the sex cells to produce male and female gametes. In this process two phases of division take place. It produces four haploid cells. Before division, genetic material of both the parents is crossed over to form new combinations in each chromosome. There are two meiotic divisions, I and II.
- S phase begins in which the DNA replicates so that two sister chromatids are formed.

The cell enters meiotic prophase whose stages are as follows-
1) Leptotene is the first stage of meiosis. In this stage, the chromosomes appear as threads.
2) Zygotene is the second stage of meiosis in which the pairing of homologous chromosomes takes place.
3) The Pachytene stage is the most important stage at which the crossing over takes place. The crossing over is facilitated by the enzymatic activity. The enzyme recombinase aids in crossing over.
4) Diplotene – In this stage the crossing over (intermixing of the parental genes) is completed.
5) Diakinesis is the condensation of chromosomes.

Thus the correct answer is A. Recombinase activity is seen in the pachytene stage.

Note: Meiosis take place in the sex cells. It involves intermixing of parental genes. DNA recombinase is used in multicellular organisms which results in the new combination of genes in the offspring.