Lecture 5 - DNA Synthesis Flashcards Preview

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Flashcards in Lecture 5 - DNA Synthesis Deck (14)
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1
Q

Semi-conservative replication

A

DNA replication results in one old strand and one new strand present in each daughter DNA molecule.

2
Q

DNA Helicase

A

Helps uncoil the DNA. Breaks Hydrogen bonds.

Enzyme that catalyses the unwinding and separating of strands in DNA replication.

3
Q

DNA Polymerase

A

Acts in 5’ to 3’ direction.
Enzyme that catalyses the formation of phosphodiester bonds between adjacent nucleotides in DNA replication.
It requires a DNA template, a DNA or RNA primer (because DNA polymerase requires an –OH on the 3’ carbon to start adding nucleotides) the four deoxyribonucleoside triphosphate (dNTP) building blocks and Mg2+ ions.

4
Q

DNA REPLICATION (4)

A

Initiates at specific sites on DNA - replication origins.
RO unwinds, forming a replication bubble allowing access to the replication machinery.
Replication bubbles will grow larger until they coalesce and form two daughter chromosomes.

5
Q

DNA Synthesis (2) B (2) M (2)

A

Occurs in S phase.
Involves complete unwinding of the parental DNA.

Bacterial cycle (M and S) - 20/30 mins
Has a single replication origin.

Mammalian cell cycle (M, G1, S and G2) - takes longer cause we have more chromosomes.

6
Q

Eukaryotic DNA polymerase

A

β - Repair
α / Δ (delta) / Ε (epsilon) - Replication
ϒ (gamma) - Mitochondrion

7
Q

Bacteria DNA Polymerase

A

I /II / Others - Repair

III - Replication

8
Q

Replication fork (5)

A

5’ - 3’
Leading strand
Continuous strand

3’ - 5’
Lagging strand
Discontinuous strand
Okazaki fragments - replication has to be originated again and again.

9
Q

Enzyme that cuts DNA strand (3)

A

Topoisomerase
Topoisomerase I - Cuts only one strand.
Topoisomerase II - Cuts both strands. Used infront of the helicase and gets rid of the coils in DNA (which becomes coiled due to helicase).

10
Q

Primase

A

Lays down some RNA (produces 3’ –OH), so that DNA polymerase knows where to start replicating.

11
Q

DNA binding proteins

A

Stabilise the single stranded DNA, stop it being re-annealed with the other parent strand.

12
Q

DNA Ligase

A

Splices the fragments together.

13
Q

Defects in DNA replication

A

Inherited defects in mismatch repair genes are involved in (colon) cancer, failure to correct DNA synthesis may lead to cancer. Error prone cell.

14
Q

DNA replication inhibitors

A

Antibacterial: Ciprofloxacin, Levofloxacin, Novabiocin (Gyrase inhibitors).
Antitumour: Etoposide, Doxorubicin, Mitoxantrone (Topo II inhibitors). Used in chemotherapy against cancers.
Antiviral: AZT (Reverse transcriptase).