mutations 3.29 recall that mutation is a rare, random change in genetic material that can be...

Mutations

• 3.29 Recall that mutation is a rare, random change in genetic material that can be inherited.

• 3.31 Understand that many mutations are harmful but

some are neutral and a few are beneficial. • 3.33 Understand that the incidence of mutations can

be increases by exposure to ionizing radiation (e.g. gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (e.g. chemicals in tobacco).

3.29 Recall that mutation is a rare, random change in genetic material that can be inherited.

• A mutation is a change in the DNA of a cell.• It can happen in individual genes or in whole

chromosomes. • Sometimes, when DNA is replicating, mistakes

are made and the wrong nucleotide is used. • This results in a gene mutation and it can alter

the sequence of the bases in a gene.• This then can lead to the gene coding for the

wrong protein.

There are several ways in which gene mutations can occur:

• Duplication of a nucleotide– Nucleotide inserted twice

• Deletion of a nucleotide– A nucleotide is missed out

• Substitution of a nucleotide– A different nucleotide is used

• Inversion of a triplet– The sequence of the bases in a triplet is reversed.

3.31 Understand that many mutations are harmful but some are neutral and a few are beneficial.

• Sometimes a gene mutation can be advantageous to an individual.

• This can be due to a random mutation.• For example: a bacteria can become resistant

to antibiotics.•

3.33 Understand that the incidence of mutations can be increases by exposure to ionizing radiation (e.g. gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (e.g. chemicals in tobacco).

• Gene mutations are random events that occur is all organisms.

• The rate at which they occur can be increased by a number of agents called mutagens.

• Mutagens include:– Ionising radiation (UV light, X-rays and gamma rays)– Some chemicals

• Mustard gas• Nitrous oxide• Cigarette smoke and tar• Some chemicals from burnt food