Replication Errors

Simple Sequence Repeat (SSR)

Sequences that are repeats and highly conserved. The number of repeats of vart. Used for DNA finger printing

single stranded DNA damage repairs

mismatch excision

base excision

nucleotide excision repair

double-stranded DNA damage repairs

Homologous recombination

End joining

Proof Reading

Both polymerases recognize incorrect base pairs. Removes nucleotides and continues synthesis

Mismatch Excision Repair

Corrects replication errors. ss DNA repair

1. Incorrect base in daughter strand is recognized. Older Strand has modifications so daughter strand doesn’t

2. Nucleotides with incorrect base & surroundings nucleotides are removed

3. Gap is repaired by DNA pol delta/epsilon and ligase

Base Excision Repair

Replace a chemically changed base (C to T), ss DNA repair

1. recognize incorrect base & remove it

2. Endonuclueases remove deoxribose phosphate

3. Gap is filled with correct base by pol.

Nucleotide Excision Repair

Fix distored DNA (Thymine Dimers) ss DNA repair

1. Distortion is recognized

2. Helix is opoened

3. Endonucleases removed the damaged & surrounding nucleotides

4. Gap is repaird by DNA pol.

Homologous Recombination

Error-free repair that requires undamaged homologous chromosomes. Ds DNA repair

1. dsDNA break is recognized & exonucleases remove necleotides and leaving 3’ ss DNA overhangs

2. ssDNA searches for homologous sequences in the sister chromatid

3. Syntehsis by DNA pol using 3’ end of the broken DNA as primer & sister DNA as template

4. Ligation

5. 2 intact double-stranded DNAs

Repair by end joining

dsDNA repair that leads to error.

1. recognition of broken ends

2. exonuleases remove overhangs and make blunt ends

3. ligates