DNA Mutations

1. DNA Mutations • Mutations are changes to the genetic information of the cell. There are 2 different types of mutations • large scale – Chromosome sections • deletions, inversions, translocations, & polyploidy • point mutations – single nucleotide • Each mutation carries with it the ability to alter the phenotype of the individual and, if in the cells that create the gametes, all the offspring of the individual.

2. Point Mutations • base-pair substitutions • silent mutation - substitution that leads to the same AA • has no phenotypic effect on the individual • ex: DNA 3'-CCG-5' changes to 3'-CCA-5' • ex: RNA 5'-GGC-3' changes to 5'-GGU-3', both code for Glycine

3. Point Mutations • missense mutation - change in a base pair that leads to a new AA • can improve protein function or render it useless (most often deleterious - sickle-cell anemia) • ex: DNA 3'-CCG-5' changes to 3'-TCG-5' • ex: RNA 5'-GGC-3' Gly changes to 5'-AGC-3' Ser

4. Point Mutations • nonsense mutation - changes an AA to a stop • most often deleterious leading to a truncated (shortened) protein segment • ex: DNA 3'-TTC-5' changes to 3'-ATC-5' • ex: RNA 5'-AAG-3' Lys changes to 5'-UAG-3' Stop

5. Point Mutations • Insertions & Deletions • lead to frame shifts if the insertion or deletion if it is in an exon • these mutations are almost always disastrous to the protein being formed as it changes all codons down stream

6. Mutagens • physical and chemical agents that cause a change in DNA • physical - radiation • chemical - classified as carcinogens • Teratogen – leading to birth defects of the fetus