Variation is the differences between individuals of the same species.
Differences between the genes of the different individuals — caused by Mutations, Meiosis Division, and Fertilisation.
Examples: Blood Group, Eye Colour, Gender, Ability to Roll Tongue, Lobed / Lobeless Ear.
Mutations are generally the random spontaneous and continuous genetic changes in the DNA base sequence. Sometimes it can cause changes in chromsomes as well.
Mutations do not affect the phenotype because the altered protein still functions normally.
Some mutations create new alleles, which can lead to new phenotypes.
Most have little effects, but sometimes one gives a survival advantage. e.g., A bird with more attractive feather colour reproduces more.
Others can be harmful, such as mutation causing sickle cell anaemia**.**
– Factors increasing rate of mutation:
| Non / Ionising Radiation | Damages DNA base sequence. (UV Light | Gamma Rays, X-Rays.) | | --- | --- | | Chemicals (Mutagens) | Heavy metals such as tar in tobacco can interfere the DNA copying process. Can increase cancer risk. |
Meiosis is the division to form sex cells; gametes.
In Meiosis, homologous chromosomes exchange genes, and separate from one another, therefore, gametes will have variation in their genes.
Any 2 gametes can fuse together randomly during fertilisation,
leading to possible combinations of genes in zygote variation in genes.
Differences between the characteristics of different individuals.