When a cell divides, the process of DNA replication is very carefully controlled to preserve the genetic information encoded within the nucleotide base sequence.

However, changes in the genome do occur. These are known as mutations. Mutations can have two results:

  • no protein is expressed
  • an altered protein is expressed

Some mutations can affect a few bases – these are single gene mutations.

Some mutations can affect the structure of one or more chromosomes - these are chromosome structure mutations.

Single gene mutation and chromosome structure mutation