Question

Arrange the following events of meiosis in correct sequence.
(i) Crossing over
(ii) Synapsis
(iii) Alignment of chromosomes on the equatorial plate
(iv) Breakdown of nuclear membrane

• A. (i), (ii), (iii), (iv)
• B. (ii), (iii), (iv), (i)
• C. (ii), (i), (iv), (iii)
• D. (ii), (i), (iii), (iv)

Answer 1

The correct option is C (ii), (i), (iv), (iii)

Meiosis is a type of reductional division in which a parent cell divides to form into four daughter cells. Meiosis includes meiosis-I and meiosis-II.

Meiosis-I includes four phases - prophase-I, metaphase-I, anaphase-I and telophase-I.

Prophase-I is of long duration and is divided into five sub stages occuring in sequence - leptotene, zygotene, pachytene, diplotene and diakinesis.

During zygotene, the homologous chromosomes undergo pairing and this is called synapsis. This is followed by crossing over that occurs during pachytene.

During crossing over, the non sister chromatids of homologous chromosomes exchange the genetic material and this leads to recombination of genetic material.

During the end of diakinesis, nucleolus disappears and nuclear membrane breaks down. The cell now enters the next phase, metaphase-I.

During metaphase-I, the homologous chromosomes align in the centre on the equatorial plate.