A base change can alter a protein

1. A mutation changes the base sequence of DNA.
2. A mutation in a coding region may change a codon and therefore alter the amino acid sequence of a protein.
3. A changed amino acid sequence may alter how the polypeptide folds.
4. Different folding can change the protein's three-dimensional shape and its function.
5. If an enzyme's active site changes shape, fewer substrates bind and the reaction rate may decrease.

Non-coding mutations can change gene expression

1. A mutation in non-coding DNA can change whether a gene is switched on or off.
2. It can also change how much protein the cell produces.
3. A change in the amount of protein can alter the phenotype even when the protein's amino acid sequence is unchanged.

Mutations have different effects

1. Most mutations have no effect on phenotype.
2. A coding mutation may have no effect because the altered codon specifies the same amino acid.
3. Some mutations have a small effect, while a rare mutation may have a large harmful or beneficial effect.
4. Whether a mutation is advantageous depends on the environment.

A mutation can produce a new allele

1. A mutation within a gene creates a new allele of that gene.
2. DNA replication copies the allele so that it passes to daughter cells.
3. A mutation in a body cell is not normally inherited by offspring.
4. A mutation in a cell that forms a gamete can be inherited.

Gene and allele must not be confused

1. A gene is a section of DNA that codes for a protein or functional RNA.
2. An allele is a different version of the same gene.
3. A mutation normally creates a new allele rather than a completely new gene.