Question

Describe the state of chromosomes (e.g., position in cell, attachments, condensation), spindle, and nuclear envelope at each stage of mitosis. Similarly, name the stage of mitosis corresponding to a description of a cell’s chromosomes, spindle, and nuclear envelope.

Answer 1

Mitosis is the process of division of cells which produce two haploid cells identical to the parent cell. It involves division of nucleus ie, karyokinesis followed by division of cytoplasm ie, cytokinesis.

There are four stages in mitosis --

• Prophase
• Metaphase
• Anaphase
• Telophase

Prophase :

• Chromosome lie loose in nucleus in this stage and have two chromatids attached to Centromere
• Chromosomal material start to condense
• Centrosome start to move at opposite poles
• Asters (radiating microtubule) form mitotic spindle
• Nuclear envelope start disintegrating

Metaphase :

• Complete disintegration of nuclear envelope is seen
• Chromosome lie freely in cytoplasm
• Chromosome condensation is complete
• Chromosome have two sister chromatid
• Chromosome align themselves in centre (equator) know as metaphasic plate.
• Chromosome gets attached to spindle fibre through kinetochore
• One chromatid attached to one side of pole and other chromatid attached to pole of other side

Anaphase :

• Centromere split and chromatid separate
• Chromatid separate to form two daughter chromosome
• Chromosome start moving toward two opposite pole
• Chromosome are still attached through centromere

Telophase :

• Chromosome reach opposite pole
• Chromosome start to decondense
• By the end, decondensation is completed and get clustered
• Nuclear envelope develop again around chromosome forming two daughter nuclei.