DNA Replication

Question 1

Meselson and Stahl Experiment

Answer 1

to determine semiconservative method occurs in DNA replication; DNA first replicated in heavy (15) Nitrogen then in light (14) Nitrogen; determined by gel electrophoresis

Question 2

DNA Polymerase

Answer 2

catalyzes DNA replication, but cannot initiate DNA chains but require a primer; direction of synthesis is 5’->3’; catalyzes the peptide bond between 3’ of deoxyribose sugar and the phosphate of the incoming nucleotide

Question 3

Beta Clamp

Answer 3

helps make DNA replication fast and efficient

Question 4

Helicase

Answer 4

unwinds (unzips) DNA and creates the replication fork

Question 5

Topoisomerase

Answer 5

prevents DNA supercoiling in front of the replication fork

Question 6

Primase

Answer 6

synthesizes RNA primers

Question 7

Ligase

Answer 7

seals leftover nicks in the DNA; creates bond between OH on 3’ strand and phosphate on 5’ strand; energy from ATP required

Question 8

Single Stranded Binding Proteins

Answer 8

protect single stranded DNA

Question 9

Origin of Replication

Answer 9

where DNA replication is initiated and double strand is first unwound; prokaryotes typically have one ORI, eukaryotes typically have multiple

Question 10

Leading Strand

Answer 10

synthesized continuously in the 5’-3’ direction

Question 11

Lagging Strand

Answer 11

synthesized discontinuously with short fragments synthesized in the 5’->3’ direction using primers but overall replication continues in the 3’->5’ direction

Question 12

Pulse Chase Experiments

Answer 12

pulse treatment with radio labelled compound; chase time, then measure the labelled compound concentration in molecule of interest at different time intervals

Question 13

Okazaki fragments

Answer 13

created on the lagging strand because of replication in 5’->3’ direction