Germline cells
Germline cells are Sex cell (sperm in males and ova/eggs in females). (sperm and ova) and the stem cells that divide to form gametes.
Germline cells can divide by mitosis to produce more germline cells to maintain the A cell that contains two sets of chromosomes. chromosome number. Diploid cells have 23 pairs of homologous chromosomes.
They can also divide byReduction division in a cell in which the chromosome number is halved from diploid to haploid. to produce A sex cell (gamete) that contains one set of chromosomes. gametes.
The nucleus of a germline stem cell undergoes two divisions, firstly separating homologous chromosomes and secondly separating chromatids. Haploid gametes contain 23 single chromosomes.
Two parents are needed in The formation of a new organism by combining the genetic material of two organisms.. During this process the nuclei of the male and female Sex cell (sperm in males and ova/eggs in females). are fused in order to create a A fertilised egg cell..
This process is known as fertilisation.
The gametes contain half the number of chromosomes (they are A sex cell (gamete) that contains one set of chromosomes.). When the male and female gametes combine, they create the full complement of chromosomes (the zygote produced is A cell that contains two sets of chromosomes.) in order to create a human embryo.
Gametes are formed by a type of cell division called Reduction division in a cell in which the chromosome number is halved from diploid to haploid..
The gametes in:
- animals are sperm and eggs
- flowering plants are pollen and eggs
Meiosis
In meiosis:
- copies of the genetic information are made
- the cell divides twice to form four gametes, each with a single set of chromosomes (haploid)
- all gametes are genetically different from each other, they show variation
The cells formed in meiosis are all genetically different. This is because the chromosomes - and genes - separate and are reshuffled during the process.
| Mitosis | Meiosis |
| Produces genetically identical daughter cells | Produces genetically varied daughter cells |
| Daughter cells have a full set of chromosomes (diploid) | Daughter cells have half a set of chromosomes (haploid) |
| 2 daughter cells are produced | 4 daughter cells are produced |
| Occurs in all body cells except gamete forming cells | Only occurs in gamete forming cells |
| Mitosis | Produces genetically identical daughter cells |
|---|---|
| Meiosis | Produces genetically varied daughter cells |
| Mitosis | Daughter cells have a full set of chromosomes (diploid) |
|---|---|
| Meiosis | Daughter cells have half a set of chromosomes (haploid) |
| Mitosis | 2 daughter cells are produced |
|---|---|
| Meiosis | 4 daughter cells are produced |
| Mitosis | Occurs in all body cells except gamete forming cells |
|---|---|
| Meiosis | Only occurs in gamete forming cells |