Chapter 16: DNA Replication Flashcards
Fredrick Griffith
He took Living S cell : Mouse dead
Living R Cell: Mouse alive
Dead S Cell: Mouse Alive
Dead s Cell & Living R Cell: Mouse Dies
The S Cell’s DNA jumped to R Living making it deadly
He called this the transformative factor
Hershey & Chase Experiment
They found an isotope (S)for the protein & one for the DNA(P) to make them glow to track them from the virus to the bacteria.
When they mixed the virus and bacteria together. The bacteria glowed the color of the of the DNA.
Meaning the the DNA was the trans-formative factors
Structure of DNA
Double helix, sugar phosphate backbone, nitrogen bases interior
How far apart is the bases are from each other?
They are equally spaced from each other
Why is DNA two strands?
It’s for replication and used as a to correct errors and removal of damage to DNA
Chargaff’s Rules
DNA composition
- varies b/tw species
- all 4 bases not in equal quantity
- bases present in characteristic ratio
Humans
A: 30.9%
T: 29.4%
G: 19.9%
C: 19.8%
DNA Polymerase I
It removes the RNA primer, and replaces it with DNA nucleotide. It checks your cells don’t have any mutations.
Can only build onto 3’ end of an existing DNA strand.
Who figured out the structure of DNA?
Watson, Crick, and Franklin
How are bases arranged ?
Purine + Prymidine
What is the 3 parts of DNA nucleotide
Phosphate group PO4
Deoxyribose 5 carbon sugar
N Base
- Adenine Thymine
- Guanine Cytosine
Anti- Parallel Strands
The backbone of DNA starts opposite of each other. So, one strand starts from 3-5 while the other starts 5-3. Due to the face that DNA has direction & complementary strands run opposite direction
How to know if it’s 3-5 or 5-3 strand
If the Phosphorus is on top it is a 5-3 strand or is the first thing you see, and at the bottom there is an OH. If the phosphorus is at the bottom and OH is at the top then it’s 3-5
Purines
A & G
Pyrimidines
T & C
What pairs w/ A
T & 2 H-bonds
What pairs w/ G
C & has 3 H-bonds
1st step of Replication
Unwind DNA
The helicase enzymes unwinds DNA from the middle to both ends of the DNA
DNA strands are stabilized by the single strand binding proteins after unwinding
Helicase
Enzyme that unwinds DNA
Single- Stranded Binding Proteins
Stabilizes the DNA strands after it gets unwind by helicase
2nd Step of Replication
Build daughter DNA strand
- add new complementary bases
This is done by DNA Polymerase III can only add nucleotides to 3’ -5’ (leading strand)end of a growing DNA strand since the strand can only grows 5’—3’
— Need a starter nucleotide to bond to
Where does the energy for bonding the phosphorus group to the sugar
The nucleotides arrived as nucleosides
- DNA w/ P-P-P (ATP, GTP, TTP, CTP)
The DNA bases arrive w/ their own energy for the binding process this is used by DNA polymerase III (enzyme) to bond
How does the body help make up for the limits of DNA
On the lagging strand ( 5’-3’ ) uses Okazaki fragments in order to keep up w/ the leading strand the gaps between the fragments are joined together by ligase
Limits of DNA polymerase III
Can only build onto 3’ end of an existing DNA strand
RHA primer
built by primase serves as a starter sequence for DNA polymerase III
Why must RNA primase must exist?
DNA Polymerase III is only able to add nucleotides to an existing nucleotide chain; it can’t “start from scratch” and therefore needs RNA primer to start process
What do all DNA have in common?
Can only add to the 3’ end of an existing DNA strand
Why do chromosomes get shorter at each replication?
loss of bases at the 5’ ends in each replication
Telomeres
repeating, non-coding sequences at the end of chromosomes=protective cap
Telemerase
enzyme extends tel
