There are 2 types of variation:
Environmental variation are aquired characteristics caused by environmental factors.
Genetic variations are inherited charateristics caused by mutation or reproduction.
Inheritied characteristics are controlled by genes, which are sections of chromosomes. Chromosomes are long molecules of DNA, that are wrapped around proteins. Every human has 23 pairs of chromosomes (46 althogether) , which come equally from sperm and an egg.
Genes allow cells to make proteins, which result in characterisitics such as eye colour.
We inherit our parents characteristics as they pass on on their genes to us through fertilization.
Genetic variation between parents and offspring may be caused by:
- Crossing over. This is the exchange of parts of chromosomes and their genes between chromosome pairs.
- Gene mutations: Changes in the number of chromosomes or in the genes that chromosomes carry.
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