Genetic Variation & Control

A nucleus of a cell contains chromosomes which is made up of DNA
1. A section of DNA is called a gene
  1. Carry information that control the characteristics of an organism, different genes control the development of different characteristics
  2. During reproduction, genes are passed from parent to offspring (they are inherited)
Inheritance of genes
1. Male gamete: Sperm
2. Female gamete: Egg
3. At fertilization genes carried by the egg/sperm are mixed to produce a new individual. (Fusing of the nuclei)
  1. This mixing is completely random so produces lots of variation, even among offspring from same parents.
4. 23 pairs of chromosomes in an adult cell
Sexual/Asexual reproduction
1. Sexual
  1. Genes from egg and sperm fuse together and produce a new individual
    1. Contains genes from both parents so you have characteristics from both.
2. Asexual
  1. One parent is needed
    1. DNA will be genetically identical so there will be no variation i.e. cloning
  2. E.g. bacteria, fungi, identical twins
3. sexual: if there was a disease and there was no variation between species then they would be wiped out
4. asexual: if there is only one organism left then they can repopulate
Meiosis
1. Gametes are formed from cells in the reproductive organs by a type of cell division called meiosis.
2. The cells that are formed by meiosis have half as many chromosomes as the cell that formed them
3. Main features: the chromosomes are copied and the cell divides twice, forming four gametes

Resource summary

	Created by Bethan Clark over 11 years ago