Module 1 - Unit 2

Mutation = a change in the amount, or arrangement of, the genetic material in a cell. 

Changes which involve parts or whole of the chromosomes are known as Chromosome mutations while chnages to genes due to changes in nucleotide base sequences are known as DNA mutations.

Mutagens = substances that increases the chances of mutations. Example: Tar and Benzopyrene in tobacco smoke, UV light and (radiation) X-rays and gamma rays. The chemicals increase the chances of unstable division in cells, which leads to cancer and radiation disrupts the structure of DNA. 

Chromosome mutations: 
- Change to the structure or number of chromosomes
- Deletion, inversion, translocation, duplication
- Changes to whole sets of chromosomes = organisms have three or more sets of chromosomes. - This is called Polyploidy - occurs mostly in plants
- Changes to the number of individual chromosomes = individual organisms fail to separate during the stage of anaphase in meiosis. This is called non-disjunction. Organisms have an additional chromosome = Polysomy
- Down's Syndrome - the addition of another chromosome on the 21st pair. Causes changes to phenotype = individuals have broad, flat faces, learning difficulties and shorter life expectancy.