Question

what are the various stages of meiosis and the main event of each?

Answer 1

interphase- divided into 3 phase:

1) G1 phase- synthesis of enzymes and structural components required for the cell cycle.

2) S phase- replication of DNA

3) G2 phase- present in mitosis but generally absent in meiosis.

4) M phase- divided into M1 and M2 phase-

Meiosis 1- has 4 phases-

A) Prophase - longest phase. Recombination occurs because of crossing over. Synapsis and chiasmata formation take place

Divided into-

a) Leptotene- assembly of lateral elements of the synaptonemal complex.

Appearances of sister chromatids in a thin thread-like structure.

b) Zygotene- chromosomes line up with each other into homologous chromosome pairs. Paired chromosomes are called a tetrad.

The formation of the synaptonemal complex and synapsis occurs.

c) Pachytene- homologous recombination, including chromosomal crossover (crossing over), occurs.

Chiasmata formation takes place at the site of recombination.

d) Diplotene- the synaptonemal complex degrades and homologous chromosomes separate from one another a little.

e) Diakinesis- chiasmata clearly visible. nucleoli disappear, the nuclear membrane disintegrates into vesicles, and the meiotic spindle begins to form. Chromosomes condense further

B) Metaphase 1- the paired homologous chromosomes align along an equatorial plane that bisects the spindle.

C) Anaphase 1- Homologs are segregated but the sister chromatids remain together.

D) Telophase 1- The first meiotic division happens that produces two daughter cells with half of the number of chromosomes.

Meiosis 2- similar to mitosis. Contains 4 phase-

A) prophase 2- Nucleoli and nuclear envelop disappears. Chromosomes condense again.

B) Metaphase 2- All the chromosomes again aligned on a metaphase plate in the center of the cell.

C) Anaphase 2- Sister chromatids separate and move towards the opposite poles of the cell.

D) Telophase 2-  marked by decondensation and lengthening of the chromosomes. disassembly of the spindle. Nuclear envelopes reform. cleavage or cell plate formation. produces a total of four daughter cells, each with a haploid set of chromosomes