Answer to Question #189443 in Genetics for Sam

Question

discuss the behaviour of the chromosomes during mitosis and meiosis in each stage of cell division, including the similarities and differences between plant and animal cells. Ensure you cover: 

• Mitosis - interphase, prophase, metaphase, anaphase, telophase

• Meiosis - interphase, prophase I, metaphase I, anaphase I, telophase I, cytokinesis, interkinesis, prophase II, metaphase II, anaphase II, telophase II, cytokinesis

Answer 1

prophase – chromosomes condense; each chromosome consists of a pair of identical sister chromatids joined at the centromere.

metaphase – chromosomes line up at the middle of the cell, along the plane of cell division, pushed and pulled by microtubules of the spindle apparatus

anaphase – sister chromatids separate and migrate towards opposite ends of the cell

telophase – chromatids cluster at opposite ends of the cell and begin to decondense

cytokinesis – the membrane pinches in to divide the two daughter cells

Meiosis is necessary for many sexually-reproducing animals to ensure the same number of chromosomes in the offspring as in the parents. The act of fertilization includes two cells fusing together to become a new zygote. If the number of alleles of each gene is not reduced to 1 in the gametes that produce the zygote, there will be 4 copies of each gene in the offspring. In many animals, this would lead to many developmental defects.

Meiosis 1 separates the pair of homologous chromosomes and reduces the diploid cell to haploid. It is divided into several stages that include, prophase, metaphase, anaphase and telophase.