handout 3.3.11 - 3/3/11 1. Proofreading: DNA repair,...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
1 3/3/11 1. Proofreading: DNA repair, whereby replication errors by DNA polymerases are first removed by their 3’ to 5’ exonuclease activity and then corrected by their 5’ to 3’ synthesis 2. Photoreactivation: DNA repair, whereby the photolyase enzyme uses the energy of visible light to reverse, and thereby, remove T=T dimers 3. Heteroduplex: Double-stranded DNA, where the two strands are derived from different, parental, duplex DNA molecules 4. Genomic totipotency: Refers to the fact that all somatic cells share the same DNA, and thereby, share the same genetic potential 5. Operon: Basic unit of gene regulation in bacteria; a regulatory, functional, and structural (i.e., linked) unit of bacterial gene expression 6. Catabolite repression: Inhibition of gene expression by the end product of a degradation pathway ---------------------------------------------------------------------------------------------------------------------------------------------- DNA REPAIR 1. Many other DNA repair systems. Can depend on intact template or not. The latter systems (which are error prone) trade an elevated mutation rate for death by functioning without a template. They include the SOS system and constitute “last ditch” efforts that work when the DNA is badly damaged Can occur after replication, in conjunction with transcription, or can involve homologous recombination (as for the repair of double-strand DNA breaks due to X rays) Nonsense-mediated mRNA decay is a repair system that surveys and targets mRNA with nonsense mutations for degradation 2. Enzymes for nucleotide excision repair are under genetic control. Thus, when UV damage is excessive, expression of these enzymes increases 3. Repair enzymes are encoded by repair genes, which can mutate. Xeroderma pigmentosum is one human genetic disease where repair genes are mutated, thereby compromising DNA repair and leaving the individual vulnerable to skin tumors and cancers 4. Many DNA repair systems use the same enzymes as those for homologous recombination. Thus, DNA repair can naturally lead to our discussion about the molecular biology of recombination ---------------------------------------------------------------------------------------------------------------------------------------------- SINGLE-STRAND BREAK MODEL 1. The original and still an excellent starting point to understand the molecular biology of recombination
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/08/2011 for the course PCB 3063 taught by Professor Marta during the Spring '08 term at University of Florida.

Page1 / 3

handout 3.3.11 - 3/3/11 1. Proofreading: DNA repair,...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online