Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
11 Cards in this Set
- Front
- Back
|
What happens in Initiation of Replication: step 1?
|
ORC binds to double-strand DNA during mitosis or meiosis.
ORC makes a region of single-stranded DNA |
|
|
What happens in Initiation of Replication: step 2?
|
DNA helicase is a motor which can unzip double-stranded DNA.
Helicase binds to single-stranded DNA. Using the energy from hydrolyzing ATP, this motor pushes the other strand away. |
|
|
DNA synthesis occurs ONLY in what direction?
|
Leading strand grows 5’ to 3’
Lagging strand also grows 5’ to 3’, but in small fragments, the Okazaki fragments, that are later stitched together |
|
|
What is the function of DNA Primase?
|
It adds RNA primers to the template strand.
RNA primer provides a base-paired 3’ end as a starting point for DNA polymerase |
|
|
What is the error rate of DNA polymerase?
|
1 in 100,000 bases
|
|
|
What does DNA polymerase do to proofread?
|
Self-correcting enzyme: proofreading through a 3’>5’ exonuclease activity
1 error per 10,000,000 nt |
|
|
Why does DNA polymerase need RNA primers for synthesis?
|
An enzyme that starts chains anew cannot be efficient at self-correction
|
|
|
Why does only 5’–3’ synthesis allow proofreading?
|
Proof-reading in the hypothetical 3’-5’ direction would block elongation.
|
|
|
What is the function of DNA ligase?
|
Seals nicks between new Okazaki fragments and the growing chain.
|
|
|
What are the three steps that give rise to high-fidelity DNA synthesis?
|
5’–3’ polymerization: 1 error per 100,000 nucleotides
Proof-reading: Reduce the error rate by 1/100 Strand-directed mismatch repair: Reduce the error rate by 1/100 Total:1 error per 1,000,000,000 nucleotides |
|
|
What is strand-directed mismatch repair?
|
Mismatch proofreading proteins bind to“nicks" in newly synthesized DNA and remove the portion of that strand.
The excised portion is then replaced with the correct matching strand. |
