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Unformatted text preview: Errorfree repair mechanism.
2. Recognizes distortions in the double helix.
3. Resulting from mis
4. Removes them prior to replication.
5. Using undamaged strand as a template to guide repair
10 2A. Mismatch repair: how we repair 2A. Mismatch repair: how we repair replication mistakes 11 2A. Mismatch repair in E.coli
2A. Mismatch repair in 1. DNA is methylated at A residues in the sequence GATC. 2. Methylation occurs after replication. 3. Newly replicated DNA is hemimethylated.
4. Mismatch repair system uses methylated strand (old strand) as template to repair error.
12 Insertions / Deletions (indels) Insertions / Deletions (indels) by Replication Slippage 13 FragileX Syndrome: A Trinucleotide repeat expansion resulting from replication slippage leading to mental retardation 14 Replication Slippage:
Replication Slippage: Examples of neurodegenerative diseases involving triplet repeat expansions
• Fragile X syndrome
– Xlinked dominant, Severe mental retardation and ataxia
– CGG repeat in the 5’ untranslated region. • Huntingtons chorea
– CAG repeat in the coding region (a stretch of polyglutamines) • Friedreich’s ataxia
– Autosomal recessive – GAA repeat in an intron 15 2B. Mismatch Repair in Humans
2B. Mismatch Repair in Humans 16 3. Double Stranded Break Repair:
3. Double Stranded Break Repair:...
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- Fall '14