Question

What are chiasmata? State their significance.

Answer 1

Hint: In meiotic cell division, during prophase I Crossing occurs between non-sister chromatids of homologous chromosomes, which result in the exchange of genetic material. The point of contact is said to be chiasmata.

Complete answer:
The structure which forms the physical link of homologous chromosomes by crossover during the meiosis is known as chiasma.

Significance of chiasmata:
- It is very essential to form during cell division because it helps in the attachment of chromosomes to opposite spindles.
- If chiasmata present it helps chromosomes to divide properly.
- The alignment will happen properly if there is chiasmata during metaphase I of the meiosis.
- If chromosomes fail to form, chiasma may result in disjoining and have chances to cause aneuploidy.
- The position of chiasma may determine genetically and sometimes they present along the length or at the near of the centromere is predetermined and single.
- If it’s single chiasma one can easily locate at the end of chromosome.
- Chiasma helps to preserve the lot of genetic material which does not undergo recombination.
- Each chiasma consists of two non-sister chromatid arms.
- Chiasmata which are close to the telomere is very unstable.
- A single chiasma can link the chromosomes together
- In research, it is said that in all 23 pairs of human chromosomes chiasma form.

Additional information:
Firstly this chiasma formed into tetrads of diplotene stage in prophase I of meiosis.

Note: In meiosis of cytological favored chromosomes the distance between the chiasma can be measured. One should understand how it’s essential to form chiasma in order to prevent improper segregation.