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.

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

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

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

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

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