Question

Diagram meiosis and mitosis in a 2N cell where N equals 2. In order to distinguish between the two chromosomes, make one long and one short. Also show the nuclear membrane, the spindle fibers, and the centriole. What are the main differences between meiosis and mitosis? Suppose the "a" locus is on one of these chromosomes and the parent cell has the genotype Aa. Label the alleles on the chromosomes and show how they behave in meiosis and mitosis if there is no crossing over.

Answer 1

source://img.wizedu.com/questions/ff814420-61e6-11ed-be33-a5261b7e4765.gif?x-oss-process=image/resize,w_580

in multicellular organisms, cells multiply from a fertilised egg to many cell by cell division. according to cell theory, all cells arise from the preexisting cells (Rudolf virchow). there are 2 types of cell division: mitosis and meiosis. cell cycle is a series of of events that takes place inside a cell. cell cycle divided into 2 main stages that are 1) Interphase and 2) Mitosis. Interphase consist of G1, S and G2 phase. in this phase cell starts preparing for cell division such as DNA synthesis, protein synthesis,etc. In Mitosis phase, cell divides itself into daughter cells. it coonsist of 4 stages that are 1) prophase 2) metaphase 3) anaphase 4) telophase. during prophase, chromosome condensation takes place. In metaphase, chromosomes arranged at an equatorial plate. During anaphase, chromosome divides and start moving towards the pole, it divides at the centromere. In telophase, chromatids behave as an individual chromosome. nuclear membrane reappears and two formation of 2 nuclei takes place. Karyokinesis is followed by cytokinesis.

Meiosis is divided into 2 stage namely meiosis1 and meiosis2. Meiosis1 is a reduction division where chromosome number get halved and meiosis2 is an equational division i.e. similar to mitosis. both meiosis1 and 2 have common phases are: prophase, metaphase, anaphase and telophase. prophse of meiosis1 is a long phase that is divided into leptotene, zygotene, pachytene, diplotene and dikinesis.

Prophase I: Chromosomes form similar to prophase of mitosis. Pairing of chromosomes takes place to form homologous pairs, that results into homologous recombination. chiasmata form between the sister chromosomes,  and exchange of genetic material (crossing over) takes place there, this is one of the main reasons for the maintenance of sex as a reproductive mode.

Metaphase I: Arrangement of chromosomes takes place at the equator similar as in mitosis. sister chromosome get separated instead of chromatids.

Anaphase I: The chromosomes are reached to the opposite ends of the cell.

Because there is single set of chromosomes at each end results in single set of DNA goes into each daughter cell. Finally two haploid daughter cells are produced. 2 more cells formed from each daughter cells in meiosis2, that is similar to mitosis.
So the final results of :
Mitosis: 1 diploid cell produces 2 diploid cells for cell division.
Meiosis: 1 diploid cell produces 4 haploid cells for gamete production.