SOCR 330 Lecture Notes - Chromosome, Genomic Imprinting, Hypoxanthine
Document Summary
Change in single nucleotide pair is a point mutation. Change on one base always results in change in complementary base on opposite dna strand. Effect of point mutation varies from none to major depending on location of change in. Transitions change purine purine (a g) or pyramidine pyramidine (c t) Transversions change purine pyramidine (t a, c g, etc. ) Transitions less likely to be detected and repaired. Frameshifts have major effects: change all codons downstream. Silent mutation has no effect on gene function. Converts cytosine to uracil (c-g pair becomes a-t after replication) Also converts adenine to hypoxanthine which pairs with cytosine (a-t pair becomes g-c after replication) Proton (h+ ion) moves within thymine (keto enol form) or cytosine (amino imino form) Loss of nitrogenous base from intact double helix ( apurinic site if g or a; apyrimidinic site if c or t) Mismatched base or distortion in helix recognized by specialized endonucleases.
