Bio 111 exam 3
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Nucleic Acid Monomers
Nucleic Acid Polymers
Criteria for Genetic Material
- 1. Information
- 2. Replication (from cell-to-cell)
- 3. Transmission (generation-to-generation)
Hershey and Chase Experiment
Tested whether protein or genetic material transferred to the next cell. Tested by infecting bacteria with phages and labeling protein and DNA with different radioactive elements. Found that the protein was not transferred and only the DNA was transferred to the next cell.
- -deoxyribose, phosphate group, nitrogenous base.
- -One less oxygen than RNA
- -Nitrogenous bases= A-T, C-G
- -ribose sugar, phosphate group, and nitrogenous base.
- -One more oxygen than DNA
- -Nitrogenous bases=U-T, C-G
Watson and Crick
Credited with discovering the structure of the double helix. Found that the strands were anti-parallel. Found the base pairing were a purine+pyrimidine.
DNA Strand Structure
- -Nucleotides are hydrogen bonded
- -Phosphodiester bond links the phosphate group with the two sugars.
- -Phosphates and sugar form the backbone.
- -Bases project from backbone.
- -Directionally 5' to 3'.
The original strand of DNA.
The newly created strands of DNA.
A proposed mechanism for DNA replication that has one daughter strand running antiparellel with the parent strand and forms a double helix with another strand paired like that. (The actual mechanism)
Strands are all parent or all daughter. not the actual mechanism.
Part parent and part daughter in one strand. not the actual mechanism.
Where the DNA unwinds. Only goes one way.
One strand goes one way and the other goes the opposite way.
Binds to DNA and travels using ATP to separate strands and move the replication fork forward (unravels the DNA).
relieves additional coiling ahead of the replication fork.
Single- stranded Binding Protein
keep parent strands open to act as templates.
DNA Polymerase III
Enzyme that covalently links nucleotides together to form the DNA strands. it requires primase and makes DNA from the RNA primers. It can only synthesize protein in 5' to 3'.
Makes a complimentary primer.
Short segments of RNA (10-12 nucleotides).
- -Same direction as the fork is moving.
- -One long continuous molecule.
- -Only one primer is needed.
- -Always segmented.
- -Direction away from the replication fork.
- -Okazaki Fragments.
- -Each fragment needs a separate primer.
Small fragments of DNA that join together to form a continuous strand.
DNA Polymerase I
Makes DNA from the RNA primers.
Forms covalent bonds between the okazaki fragments.
Extra overhang on the chromosomes to make sure no important parts of DNA do not copy. They are a series of short nucleotide sequences repeated at the ends of eukaryotic chromosomes.
Why is DNA replication very accurate?
- 1. Hydrogen bonding between A and T or C and G is more stable than mismatches.
- 2. Active site of DNA polymerase is unlikely to form bonds if pairs are mismatched.
- 3. DNA polymerase removes mismatched pairs
- -Proofreading results in DNA polymerase backing up and digesting linkages.
- -other DNA replication enzymes.
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