6.3 - Mutations

What a mutation is

• A mutation is a random change to the DNA - a change to the sequence of bases, or to the structure of a gene.
• Mutations happen continuously and at random - for example, when DNA isn't copied perfectly as a cell prepares to divide.
• A mutation can sometimes be passed on from a parent to its offspring.
• A mutation produces a genetic variant - a different form of the gene, also called a new allele.

How mutations affect the phenotype

• The phenotype is the organism's observable characteristics.
• Most mutations have no effect on the phenotype at all - these are described as neutral.
• Some have a small effect, altering a characteristic only slightly.
• Very rarely, a single mutation has a significant effect and produces a noticeably different characteristic.
• The ones that change anything obvious are a tiny minority of all the mutations an organism carries.