MUTATIONS

Mutations are heritable changes in genetic information Only mutation in the GAMETES can be passed on from generation to generation There can be point mutations and chromosomal mutations

Point Mutation A gene mutation that involves changes in one or a few nucleotides. They occur at a single point in the DNA sequence There are three types:  Substitutions  Insertions  Deletions The generally occur during replication – any subsequent cell that came from the original cell can be effected

Substitutions One base is changed to a different base Usually effect no more than one amino acid Sometimes have no overall effect ( silent mutation)

Insertions and Deletions Point mutation in which one base is removed or inserted from the base sequence Effects can be dramatic Because the code is read in groups of 3 (codon), adding or removing a base would shift every codon that follows the mutation These are also called FRAMESHIFT mutations because they shift the “reading frame” of the genetic message Can alter a protein so much that its unable to perform its function

Chromosomal Mutations Involve a change in number or structure of chromosomes Can change the location of genes on chromosomes, and the number of copies of some genes

Mutagens A chemical or physical agent in the environment that could cause a mutation. Examples include:  Tobacco smoke  X-Rays  Environmental pollutants  Pesticides Cells can sometimes repair the damage; but when they can’t, the DNA sequence is permanently altered.

Harmful vs. Helpful Mutations Harmful mutations are those that dramatically change protein structure or gene activity Can disrupt normal biological activity and cause genetic disorders (like Sickle cell anemia) and cancer Helpful mutations help drive evolution Proteins produced with new or altered functions can be useful in a changing environment Example: insects resisting pesticides