Mutations

Mutations:

• the arrangement of bases in an individual gene = DNA mutations
• the structure of the chromosome (changes the arrangement of the genes) = chromosome mutations 
• a change in a cell which changes a trait - usually a change in a gene sequence e.g.
• ...AACTAGGGACATTTACG
• ...AACTAGGGCAATTTACG
• can also be gene loss

Causes of mutations:

• radiaition e.g. to UV
• Chemicals e.g. cigarette smokes
• spontaneously 

Types:

• In body cells - can lead to cancer
• In sex cells - can lead to new traits in offspring

• Mutations can occur in gametes and somatic cells
• chance of mutations is between 2-30x10^-7
• faulty DNA can be repaired by specific enzymes
• unrepaired mutations will affect new proteins being synthesised

Point mutations are caused by changes in an individual gene due to miscopying of one or more nucleotides.

Deletion or insertion of a nucleotide result in a frame-shift.

Substitution mutation result in a change of one base

Some mutations can be harmful, beneficial or neutral.

e.g.

Dark skin

- in Africa protects against UV light - less chance of skin cancer

- however, prevents limited amount of UV light reaching skin cells to synthesise vitamin D - could lead to rickets, narrow pelvis (difficulty in child birth) and increased risk of hear disease and cancer