ICSE Class 10 Answered

• Meiosis-II resembles mitotic division.
• In this division, the two chromatids of each chromosome separate from each other and go to separate daughter cells.
• The number of chromosomes remains the same as produced by meiosis-I.
• Meiosis-II consists of four stages—prophase-II, metaphase-II, anaphase-II and telophase-II.

Prophase-II

• During prophase-II, the already duplicated centrioles move in pairs to the opposite poles.
• Each pair of centrioles develops astral rays round it to form an aster.
• A spindle is laid down between the two pairs of centrioles.
• The nuclear membrane and the nucleolus disintegrate and disappear.
• The chromatin fibres undergo compaction and appear in the form of distinct chromosomes.
• Each chromosome consists of two chromatid threads joined by a centromere.

Metaphase-II

• During metaphase-II, the chromosomes come to lie on the equator of the cell and form a single equatorial or metaphasic plate.
• The spindle fibres become attached to both kinetochores of the centromere of each chromosome.

Anaphase-II

• During anaphase-II, the two chromatids of each chromosome start moving away from each other.
• They reach the poles of the spindle where they are called chromosomes.
• Each pole has a haploid number of chromosomes and haploid amount of DNA.

Telophase-II

• During telophase-II, the daughter chromosomes on the opposite poles decondense to form
  chromatin fibres.
• The nuclear envelope develops from the endoplasmic reticulum and the new nucleolus reorganises.
• The spindle fibres and astral rays disintegrate and disappear.
• This marks the end of telophase-II and karyokinesis of meiosis-II.

Cytokinesis-II

• Cytokinesis follows karyokinesis of meiosis-II.
• The cytoplasm divides in the middle by furrowing in an animal cell and by cell plate formation in a plant cell.
• At the end of cytokinesis, two daughter cells are formed, each with half the number of chromosomes and half the amount of nuclear DNA of the parent cell.
• Cytokinesis may occur successively after each nuclear division.
• The diploid parent cell divides first by heterotypic division into two haploid cells, which then produce four haploid cells by homotypic division.
• The four daughter cells may form a linear or isobilateral tetrad.