- Random change in DNA sequence or genetic material
- types of mutations
- gene: changes in a single gene
- chromosomal: changes in the whole chromosome
- caused by errors in
- replication
- transcription
- cell division
- External agents (mutagens)
- chemicals
- Radiation
- Viruses
- point mutations
- occur at a single point in the DNA sequence
- DNA → TAC GCA TGG AAT
- RNA → AUG CGU ACC UUA
- AA → MET ART THR LEU
- A substitution occurs and C is being substituted with T
- DNA → TAC GTA TGG AAT
- RNA → AUG CAU ACC UUA
- AA → MET HIS THR LEU
- Frameshift mutations
- occurs when a nucleotide is deleted or inserted in a DNA strand
- Bases are still read in groups of 3, so.. it shifts the reading of all of the codons from that nucleotide on
- DNA → TAC GCA TGG AAT
- RNA → AUG CGU ACC UUA
- AA → MET ART THR LEU
- But how does this affect the proteins being made?
- DNA → TAT CGC ATG GAA T
- RNA → AUA GCG UAC CUU A
- AA → ILE ALA TYR LEU
- Insertion and deletion
- Chromosomal mutations
- changes in number or structure of chromosomes
- result: change in location and/or number of genes
- Types of chromosomal changes:
- Deletion: loss of all or parts of a chromosome
- Duplication: extra copies of parts of a chromosome
- Inversion: reverse the direction of part of a chromosome
- Translocation: part of one chromosome breaks off and attaches to a different chromosome
- significance of Mutations
- neutral- Many have little or no effect
- Harmful- dramatic changes in protein structure or gene activity
- defective proteins that disrupt normal biological activity
- Beneficial- mutations are the source of variation
- some lead to a characteristic that helps an organism survive better in a changing environment
- Impact on offspring
- mutations can happen in both body cells and gametes (germ cells)
- Body cell mutations
- only affect organism
- Germ cell mutations
- passed onto offspring
- source of genetic variation