Question

From the following identify the two correct statements with reference to meiosis-I
I. Bead like structure are absent on chromosomes.
II. Displacement of chiasmata occurs in diakinesis.
III. Separation of two basic sets of chromosomes.
IV. No division of centromere.
The correct statements are :

• A. II,III
• B. II,IV
• C. III,IV
• D. I,III

Answer 1

Answer: (A)

Meiosis is a complex type of cell division, which encompass two successive divisions of the cell, thereby forming 4 cells from a single parent cell. The following are the characteristic features of the division:

1. there is reduction in the chromosome number in meiosis-I.
2. there is genetic recombination or crossing over.

Prophase-I of meiosis-I is the longest phase in which there are five sub-phases, leptotene > zygotene > pachytene > diplotene > diakinesis. The salient features of these sub-phases are:

• In leptotene, chromosomes condensation is completed.
• In zygotene, the synapsis of homologous chromosomes takes place and tetrad formation occurs.
• In pachytene, there is crossing over.
• In diplotene, chiasmata formation is prominent.
• In diakinesis, terminalization of chiasmata take place.

In the anaphase-I of meiosis-I, the homologous chromosomes separate and one of the two moves to the opposite poles. This reduces the total number of chromosomes from 2n to n. Thus, each pole receives only one of the two homologous chromosomes.
There is no centromere division in meiosis-I. However, in meiosis-II, there is centromeric division thus, ensuring no further reduction of chromosomes in the daughter cells.
Beads like structures are present on chromosomes during meiosis.