Biology 1001A Lecture Notes - Lecture 3: Dna Mismatch Repair, Transposable Element, Dna Ligase

• School: Western University
• Department: Biology
• Course: Biology 1001A
• Professor: Tom Haffie

Document Summary

Dna polymerase iii makes mistake, cannot move forward because 3" oh is in wrong position, uses deoxyribosnuclease (exonuclease activity) to break the hb between base pairs, and add on the correct base pair: mechanism of mismatch repair. Repair enzymes check along the dna strand for helical deformities (where bases are paired incorrectly), will cause distortion of dna helical shape. The enzymes break phosphodiester bonds that contain the mismatch, dna polymerase iii re-fills the gap, and dna ligase seals the nick: difference between insertion sequences, transposons and retrotransposons. Insertion sequence- simplest transposable elements, gene code only for transposase. Transposons- is at two ends, contain coding genes between them, which is also moved when it is transposed. Retrotransposons- uses a rna template (rna polymerase) to create the new copy of dna, insert into other place of genome: why mobile elements are considered to be biological mutagens.