Mutations may be spontaneous (i.e. arise naturally as random errors in DNA) or induced (i.e. deliberately or accidentally produced by chemicals or radiation).
Mutagens are chemicals or forms of radiation that cause mutations.
Two Types of Gene Mutations
Replacement of one nucleotide by another (also called Point Mutation) may lead to:
No change in the protein formed
Change in an amino acid and protein
Non-functional protein or incomplete protein if a stop codon is formed
Addition or deletion of a nucleotide will probably cause a non-functional protein.
Types of Chromosome Mutations
Changes in the Number of Chromosomes can be of two types:
Polyploidy - is a condition of having extra sets of chromosomes to make organisms such as plants tetraploid (4n). This is an advantage in plants as cells are larger.
Aneuploidy - is a condition of the gain or loss of individual chromosomes. Examples include Downs' Syndrome (extra No. 21 chromosome), Turner Syndrome (extra X chromosome in a female), and Klinefelter Syndrome (extra X chromosome in a male).
