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
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.
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