Differences within a population are called genetic variation
Phenotype
The characteristics that an organism displays
Environmental factors can also influence phenotype
Mutations mean that the gene is altered, producing a genetic variant
Some variants have a small influence on the organism's phenotype
The genetic disorder cystic fibrosis is caused by a mutation with a huge effect on phenotype
Organisms of the same species havedifferences
Mutations occur continuously
Genotype
All of the genes and alleles that an organism has
Very occasionally, variants can have a dramatic effect on phenotype
Speaker: 'My mum's got no trousers - cos I've got her jeans... you can't blame all of your faults on your parents - the environment usually plays a role too'
Variation can be caused by differences in genotypes
An organism's genotype affects its phenotype
Through interactions with its environment and conditions in which it lives
An organism's genes are inherited from its parents
Not all people are identical
Most mutations have no effect on an organism's phenotype
Some characteristics are controlled by multiple genes
Most mutations have little or no effect on the protein the gene codes for
