Question

 What is the overall purpose of mitosis?

 What is the function of meiosis? In what type of cells is meiosis observed?

 In what types of organism(s) does mitosis occur? What type of cell division occurs in bacteria?

 What controls Mitosis? Checkpoints in the normal cell cycle prevent cells from going through division if problems occur-for example, if the DNA is damaged.

 How does meiosis increase genetic variation?

Answer 1

1) The overall purpose of mitosis are cellular reproduction and general growth, cell replacement, asexual reproduction, identical copies ,and energy storage.

Development and growth - Mitosis is part of the process of cell division. Mitosis is important for cells to reproduce, whether they are a single-celled organism or part of a multi-celled organism which requires to grow. For organismal growth, mitosis produces more cells of the same type, which can act the same function in an organ.

Cell replacement - This occurs when the original cell is damaged or wounded. New cells are formed to replace those which were damaged. Examples of this are the healing of a cut or a broken bone. When old cells die, new ones replace them to ensure continuing functionality.

Asexual reproduction - Single-celled organisms and certain multicellular organisms use mitosis for asexual reproduction.

Identical copies - The purpose mitosis is one cell to produce into two identical cells. A cell does this by replicating its DNA, which carries the information . DNA replication happens during interphase of the cell cycle. Mitosis is a multi-step process which divides a cell's duplicated DNA between two cells and each will have the same amount of DNA as the original cell.

Energy storage - Organisms have the ability to store energy for later use. Excess food is converted to chemical energy, one form of which are triglycerides known as molecules of fat. Cells that store fat are called adipocytes. Under conditions of excess food consumption, adipocyte stem cells go through mitosis to make copies of themselves. These copies then differentiate, or mature, into storage cells which enlarge as they collect fat molecules.

2) The function of meiosis: a Sexual Reproduction

                                             b. Reduces the chromosome number from diploid to haploid.

                                             c. Ensures that each of the 4 gametes has a complete set of chromosomes.

In meiosis cells split to form new cells with half the usual number of chromosomes, to produce gametes for sexual reproduction. This process occurs in gamete, or sex, cells.

3) Mitosis occurs in all eukaryote celleullar organisms. Mitosis generate two identical cells from one mother cell.

Bacteria divide by binary fission. Binary fission is a form of asexual reproduction where identical bacteria is formed from another previously existing one.

4)Cell cycle checkpoints are control mechanisms in eukaryotic cells which make sure proper division of the cell. Quality control’ will check the overall ability of the cell to enter mitosis process. These controls control to support the cell division programme and prevent damage to the genome. If DNA is not too damaged a repair may be possible and the cell cycle hold and slowed down until repairs are effected. Cell cycle ‘quality control’ may determine that the damage cannot be repaired.

5) Genetic variation is increased by meiosis. During fertilisation, one gamete from each parent combines to form a zygote,Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote. Recombination occurs in prophase I, during which the sister chromatids cross over and overlaps where exchange of DNA fragments in the cell occurs. This leads to large number of different combination of genes, which were not present in the parents.