Ch. 16 and 17 Review Flashcards
(49 cards)
What are the components of a chromosome?
- DNA
- Protein
In the 20th century, scientists believed what macromolecule encoded for genes?
Protein
When was the conformation of DNA known?
1950s via Watson and Crick
State Chargaff’s rule
A=Tor U
G= C
ratios of these purines and pyrimidines are equal
What did Watson and Crick conclude about DNA?
-DNA forms a HELIX with UNIFORM WIDTH (2nm)
-DNA has TWO polynucleotide chains
-The backbones are on the outside, bases on the inside
-H bonds hold bases together
How many bonds do the purines form?
Adenine forms 2 bonds, Guanine forms 3
DNA strands are _______
Antiparallel, strands run opposite from each other
Are DNA strands identical?
NO, they’re complimentary meaning 4 of nucleotide base pairs are possible
DNA must be copied because it encodes for what?
DNA encodes proteins and traits
How does the cell synthesize DNA
- Two strands separated
- Each strand used as a template to build new strands USING complementary base pairing
What happens to the original DNA?
It’s present in daughter cells but no longer intact. Semiconservative DNA.
Where does the energy for making DNA come from?
From the nucleotides bearing 3 phosphates. recall phosphates are covalently bonded, when broken they release a lot of energy. Nucleotide brings the energy NOT ATP.
DNA replication must be? What is the solution?
- accurate and efficient
occur at manly sites simultaneously
What is a replication bubble? Where are the forks?
Replication bubble on the origin of replication where new DNA is synthesized.
The forks are the ends of the bubble
What is needed to make DNA?
- 2 template strands
- Nucleotides
- Several enzymes and proteins (made during G1)
DNA polymerase adds to which DNA end?
3’ end
DNA is always built from 5’ to 3’
Which way are DNA template strands read?
3’ to 5’
Does DNA polymerase initiate polynucleotide synthesis?
NO, other enzymes do this using an RNA primer
What are the 1-2 steps of DNA replication?
- DNA helicase unzips DNA
- Single Strand Binding Protein stabilizes broken DNA strands (STICKY)
What are the steps for leading strand DNA synthesis?
3a. RNA primase makes RNA primer for DNA leading strand
3b. DNA polymerase moves towards the fork and makes DNA 5’ to 3’
What are the steps for lagging strand DNA synthesis?
4a. RNA Primase makes RNA primer for lagging strand
4b. DNA polymerase makes DNA away from the fork going 5’ to 3’
4c. Repeat steps previous steps (primer –> extend –> unwind)
lagging strand always moves away from the fork in many pieces called Okazaki fragments
How do you join Okazaki fragments?
via hydrolytic enzymes
enzymes remove RNA fragments and extend Okazaki fragment through the primer
Ligase will join the missing section of DNA via a covalent bond
Summarize the steps of DNA synthesis by concept only
- Helicase
- Single Strand Binding Protein
Leading Strand
3a. Primase
3b. Leading strand synthesis
Lagging strand
4a. Primase
4b. Lagging strand synthesis
5. primer placement
6. DNA ligase
What are the rules of DNA code?
- codons must occur in series
- codons cannot overlap
