Mutations TSW identify and describe the various types of mutations and their effects

Gene Mutations Produce changes in a SINGLE gene Point Mutation: involve changes in one or a few nucleotides Occurs @ a single point in a DNA sequence

Substitutions 1 base is changed to another Usually affects no more than 1 amino acid Example: T A C G C A T G G A A T T A C G T A T G G A A T

Insertions 1 base is inserted into a DNA sequence Usually has more dramatic effects Example: T A C G C A T G G A A T T A T C G C A T G G A A T

Deletions 1 base is removed from a DNA sequence Usually has more dramatic effects Example: T A C G C A T G G A A T T _ C G C A T G G A A T T C G C A T G G A A T

Frameshift Mutations Shift the “reading frame” of a genetic message May change every amino acid that follows the mutation May make a protein unable to perform its original function

Chromosomal Mutations Involve changes in the # & structure of chromosomes May change the location of genes on a chromosome May change the # of copies of some genes

1. Deletions Lose ALL or part of a chromosome

2. Duplications Produce extra copies part of a chromosome

3. Inversions Reverse the directions of parts of a chromosome

4. Translocation One part of a chromosome breaks off & attaches to another

Significance of Mutations Most are neutral (have little or no effect on gene expression or protein function) Some are harmful (cause genetic disorders & cancer) or even lethal Some are beneficial (source of genetic variation)

Polyploidy Beneficial mutation Extra set of chromosomes (3N or 4N) Often larger & stronger than 2N