Question

Compare and contrast the processes of mitosis and meiosis. Describe the overall processes (not each detail) and explain why each is important. Be sure to include what type of cell (diploid of haploid) each process starts with, in what location of the body it takes place, and the end result (what is produced)? Please note in a diagram or in words whether or not the beginning cell and the final cells contain sister chromatids and/or homologous chromosomes.

Answer 1

Mitosis is asexual reproduction or somatic cell division in which the diploid parent cell divides into two diploid daughter cells. The mitosis is carried out in four stages known as prophase, metaphase, anaphase and telophase.

Prophase: The nucleolus is disappeared and the nuclear envelop is fragmented. The spindle fibers attached to the chromosomes at the centromere. The chromosomes are pulled to the poles.

Metaphase: During this phase the chromosomes are arranged at spindle equator that is the midpoint between the spindle poles. The spindle fibers extend up to opposite poles and the unattached spindle fibers overlap behind the equator.

Anaphase: During this phase, the sister chromatids separate apart to become the daughter chromosomes. The attached spindle fibers disassembled and at each pole a daughter chromosome is formed. The spindle fibers move apart so that the separation of chromosomes occurs.

Telophase: During this phase, the spindle fibers disappear and the nuclear envelop is formed around each daughter chromosome. Each nucleus consists of same number and type of chromosomes similar to the parent cell.

Cytokinesis: After the division of nucleus the division of cytoplasm takes place and the daughter cells are completely apart from the parent cell. In some cases the division of cytoplasm does not take place and only mitosis is continued resulting in a multinucleated cell.

Meiosis is reduction division taking place in diploid cells. During meiosis two consecutive nuclear divisions take place and result in formation of 4 haploid daughter nuclei. The meiosis is carried out in series of events occurring at various stages. In the first stage (prophase I) the diploid nuclei containing chromosomes from as tetrads and are condensed. The synapsis and crossing over takes place to exchange the fragments between the chromosomes.

During metphase I the tetrads are arranged at the spindle equator facing the opposite spindle poles. During anaphase I the tetrads are separated and resulting in the movement of dyads to the opposite poles. During telphase I the haploid daughter nuclei receive two chromosomes one from each homologous pair.

During the meiosis II the chromosomes are condensed, the fragmentation of nuclear envelope takes place at prophase II stage. During metaphase II the sister chromatids or dyads are arranged at the spindle equator facing the opposite spindle poles. During anaphase II separation of sister chromatids occur and the daughter nuclei move to the poles. During telophase II 4 haploid daughter nuclei are resulted and these are genetically different from the parent nuclei because of the crossing over event.