Question

Genetic recombination occurs in_____phase of prophase of meiosis I.
A) Leptotene
B) Zygotene
C) Pachytene
D) Diplotene

Answer 1

Hint: Genetic recombination is a process that refers to the rearrangement of DNA sequences by undergoing breakage and then rejoining the chromosome segment. It takes place during the meiosis in humans and the information is passed on from parents to the offspring.

Complete answer:
Genetic recombination occurs in the Pachytene phase of prophase of meiosis I. So, the correct option is (C).
Meiosis - It occurs in the mature diploid reproductive cells in which the nucleus divides twice but the chromosome replicates only once to form four haploid cells.
It is further of two steps-
• Meiosis I
• Meiosis II
Meiosis I results in the formation of two haploid cells from diploid cells. It is of four phases-
• Prophase I-It is the longest phase and contains 5 subphases.

> Leptotene- Chromosomes are long and thread-like. It also has definite polarisation and the stage is referred to as the bouquet stage.
> Zygotene- Pairing or synapsis of homologous chromosomes occurs in this stage. Paired chromosomes are called Bivalents. Synaptonemal complex(nucleoprotein complex, adherence of visible sister chromatids) formation takes place.
> Pachytene- In this crossing over takes place. The exchange of chromatids between non-sister chromatids (chromatids belonging to the different chromosomes of homologous pairs) occurs at this stage. Due to this genetic recombination occurs.
> Diplotene- Paired chromosomes begin to separate- Desynapsis occurs. Homologous chromosomes drift away and remain joined to one another at specific points called Chiasmata.
> Diakinesis- Formation of spindle occurs.
Then, prophase I is finished and it is followed by-
• Metaphase I
• Anaphase I
• Telophase I
• Meiosis II

Additional information: Recombination also occurs in mitosis in eukaryotes after replication. If genetic recombination does not happen then the species is less prone to variation.


Note:
Some important information-
> Genetic recombination occurs in both Mitosis and Meiosis and the stages along with the changes for both are different.
> All the stages and the phenomenons that take place in meiosis are important.
> Also, gene conversion is a part of genetic recombination and not a separate process.