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Variation and mutation
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No two people are exactly alike. Variation comes from genes, the environment, or both.
Causes of variation
Genetic variation: inherited, for example blood group and eye colour.
Environmental variation: caused by surroundings, for example scars or language spoken.
Most characteristics, like height and weight, are affected by both.
Environmental variation: caused by surroundings, for example scars or language spoken.
Most characteristics, like height and weight, are affected by both.
Mutations
A mutation is a change in the DNA base sequence.
Most mutations have no effect. A few change a protein, which can be harmful or, rarely, useful.
Mutations create new alleles and are the source of genetic variation.
Most mutations have no effect. A few change a protein, which can be harmful or, rarely, useful.
Mutations create new alleles and are the source of genetic variation.
The Human Genome Project
Scientists mapped the whole human genome, published in 2003.
It helps identify genes linked to diseases and develop new treatments.
It helps identify genes linked to diseases and develop new treatments.
Identical twins grow up in different countries and end up different heights. What does this show?
- Identical twins have the same genes.
- So the height difference must come from the environment, such as diet.
Answer: The environment affects height.
Variation can be genetic, environmental or both. Mutations are changes in DNA; most have no effect. The Human Genome Project mapped human genes.
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