Chromosome mutations are due to change in either the chromosome structure or the chromosome number of a cell.

A gene mutation is a change in the order of bases on a strand of DNA.

Factors that increase the chances of mutation are called mutagens.

Mutagenic agents:

Gene and chromosome mutations occur naturally and generally have a low frequency. However, certain chemicals and rays can increase the rate of frequency of mutation. These are called

mutagenic agents and include:

chemicals such as mustard gas, caffeine and cochineal

irradiation such as U-V radiation, X-rays and gamma rays


Mutations happen naturally but the mutation rate is increased if organisms are exposed to mutagens.

Causes & Effects


Mutations in DNA sequences generally occur through these processes:

• DNA damage from environmental agents such as ultraviolet light (sunshine),

• nuclear radiation (e.g. Chernobyl incident?),

• Mistakes that occur when a cell copies its DNA in preparation for cell division.

• Certain factors can damage DNA by altering nucleotide bases so that they look like other nucleotide bases.

• When the DNA strands are separated and copied, the altered base will pair with an incorrect base and cause a mutation.


–Production of new/ superior protein

Results; gain on reproductive advantage

–Neutral mutation

Results; no change

–Production of inferior or no protein

Results; fatal and/or disease causing