BIO Chapter 16

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Watson and Crick

figured out the structure of DNA
Chargaff's Rule
- In any species is an = number of A and T bases and an = number of C and G bases
- Chargaff's rule expands on complementary base pairing
Purines pair with pyridimines
- Purine + purine: too wide
- Pyridimine + pyridimine: too narrow
- Purine + pyridimine: width consistent with x-ray data
Complimentary base pairing

Watson-Crick's base pairing model explains Chargaff's rule
Daughter strands
- 1/2 parent, 1/2 new
- 2 new daughter strands are built based on the base-pairing rule
DNA replication

starts replicating at many different spots for efficiency
Helicases
- enzymes that untwist the double helix at the replication forks
- "Helicase unzips the suitcase!"- Jenna
Single-strand binding protein

binds to and stabilizes single-stranded DNA until it can be used as a template
Topoisomerase
- corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands
- stabilizes double helix part
RNA primer
- starts the replication process
- brought in by primase
DNA polymerase
- catalyzes elongation of new DNA at a replication fork
- attaches free nucleotides to the strand
Antiparallel elongation
- DNA polymerases add nucleotides only to the free 3' end of a growing strand (<-- replication is only allowed to proceed in one direction)
- 5' and 3' strands end on different things (5' ends on phosphate, and 3' ends on hydroxide) and they run anti-parallel to each other
Okazaki fragments
- joined together by DNA ligase
- series of segments that synthesizes the lagging strand
Mismatch repair

repairs enzymes; corrects errors in base pairing
Nucleotide excision repair

nuclease cuts out and replaces damaged stretches of DNA
Telomeres

nucleotide sequences that postpone the erosion of genes near the ends of DNA molecules

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Card Set

BIO Chapter 16

Description

Chapter 16: Molecular basis of inheritance

Updated

2010-12-12T20:41:05Z

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