Give the differences in Mitosis and meiosis.?

Question

neede for my biology class

Answer 1

While mitosis and meiosis both involve replication of the DNA and production of daughter cells, there are several major differences with respect to how each process is performed and the identities of the cells that result.

Mitosis is the division of somatic (body) cells... If you cut your finger, for instance, the new skin that was formed resulted from mitotic divions. Similarly, when blood cells die (from age) the hematopoietic stem cells in your bone marrow divide to give rise to new blood cells. Mitosis proceeds as follows:

When a cell decides it is time to divide, it initiates a series of steps that result in replication of the genome (all the chromosomes). A normal non-mitotic human cell has 46 chromosomes (23 pairs)--during the initial phases of mitosis, there are twice this many (92). One set of each chromosome is pulled toward opposite poles of the cell, and then the cell divides--resulting in two identical cells, each with a complete complement of the genome.

Meiosis, on the other hand, is how organisms form sex cells (sperm and eggs). Meiosis is a process of reduction--since an organism has a set number of chromosomes that it needs in order to function properly, it must have a method by which to reduce the chromosome number to half in order to facilitate sexual reproduction. If this did not occur, each subsequent generation would have twice the number of chromosomes than the previous generation. So, in humans, who have 46 chromosomes, we need to maintain this through each generation--so, when males and females undergo gametogenesis (spermatogenesis and oogenesis respectively), they reduce the number of chromosomes in their sex cells to 23--thus, when they reproduce (the union of a sperm and an egg), the resulting embryo will have the normal number of chromosomes (23+23=46). Meiosis proceeds as follows:

Replication of the genome occurs as in mitosis--the chromosomes then separate to the poles (after something called crossing-over occurs (this is complex, but let me know if you would like it explained))... Two cells result that still have 46 chromosomes but have exchanged some parts of non-homologous chromosomes (in order to increase genetic diversity). These two cells then enter another round of division--except no replication occurs this time. When it comes time to separate, the chromatids (half of the maternal/paternal chromosome pairs) are pulled to opposite parts of the cell. This results in four cells with 23 chromosomes (chromatids)--half of the normal number. After union of two gametes, a viable, genetically complete embryo is formed


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Major differences between mitosis and meiosis.

1. Number of cell divisions and products.
mitosis - one cell division resulting in two daughter cells
meiosis - two cell divisions resulting in four products of meiosis


2. Ploidy (# chromosome sets) per nucleus.
mitosis - 2N to 2N
meiosis - 2N to N to N

3. Synapsis of homologous chromosomes.
mitosis - no pairing
meiosis - pairing at zygotene of prophase I

4. Exchange of genetic material between synapsed homologous chromosomes.
mitosis - does not occur
meiosis - occurs at pachytene of prophase I (first visible at diplotene)

5. Timing of division of centromeres.
mitosis - occurs at anaphase
meiosis - occurs at anaphase II but not at anaphase I

6. Genetic variation.
mitosis - conservative process; does not lead to genetic variation
meiosis - leads to increased genetic variation following recombination (crossing-over)

Answer 2

While mitosis and meiosis both involve replication of the DNA and production of daughter cells, there are several major differences with respect to how each process is performed and the identities of the cells that result.

Mitosis is the division of somatic (body) cells... If you cut your finger, for instance, the new skin that was formed resulted from mitotic divions. Similarly, when blood cells die (from age) the hematopoietic stem cells in your bone marrow divide to give rise to new blood cells. Mitosis proceeds as follows:

When a cell decides it is time to divide, it initiates a series of steps that result in replication of the genome (all the chromosomes). A normal non-mitotic human cell has 46 chromosomes (23 pairs)--during the initial phases of mitosis, there are twice this many (92). One set of each chromosome is pulled toward opposite poles of the cell, and then the cell divides--resulting in two identical cells, each with a complete complement of the genome.

Meiosis, on the other hand, is how organisms form sex cells (sperm and eggs). Meiosis is a process of reduction--since an organism has a set number of chromosomes that it needs in order to function properly, it must have a method by which to reduce the chromosome number to half in order to facilitate sexual reproduction. If this did not occur, each subsequent generation would have twice the number of chromosomes than the previous generation. So, in humans, who have 46 chromosomes, we need to maintain this through each generation--so, when males and females undergo gametogenesis (spermatogenesis and oogenesis respectively), they reduce the number of chromosomes in their sex cells to 23--thus, when they reproduce (the union of a sperm and an egg), the resulting embryo will have the normal number of chromosomes (23+23=46). Meiosis proceeds as follows:

Replication of the genome occurs as in mitosis--the chromosomes then separate to the poles (after something called crossing-over occurs (this is complex, but let me know if you would like it explained))... Two cells result that still have 46 chromosomes but have exchanged some parts of non-homologous chromosomes (in order to increase genetic diversity). These two cells then enter another round of division--except no replication occurs this time. When it comes time to separate, the chromatids (half of the maternal/paternal chromosome pairs) are pulled to opposite parts of the cell. This results in four cells with 23 chromosomes (chromatids)--half of the normal number. After union of two gametes, a viable, genetically complete embryo is formed.

Answer 3

Meiosis is important in assuring genetic diversity in sexual reproduction while Mitosis is just the cell division.