DNA Replication

Question 1

Semi-Conservative Replication

Answer 1

-each parental strand serves as a template for the synthesis of a new daughter strand using the base-pairing rules

Question 2

Conservative Model

Answer 2

two parental strands stay together

Question 3

Dispersive Model

Answer 3

all four strands somehow combine into a mixture of old and new DNA

Question 4

Meselson & Stahl

Answer 4

• centrifuged DNA so the light isotope is at the top and the heavy is at the bottom
• when replicated the band was in the middle indicating a hybrid of the 14N and the 15N

Question 5

Replication Forks

Answer 5

separation of parental strands

Question 6

Leading Strand

Answer 6

replication in the 5’ to 3’ direction is continuous and only one primer is needed

Question 7

Lagging Strand

Answer 7

• discontinuous strand
• contain okazaki fragments
• can’t be replicated until enough of the template DNA is revealed
• requires post-replication processing
• DNA ligase is able to join 3’ end of a fragment to an adjacent nucleotide by catalyzing the phosphodiester bond joining the okazaki fragments together

Question 8

DNA Replication

Initiation

Answer 8

• DNA helicase are able to bind to parental DNA and initiate the unwinding of the DNA double helix and does so by breaking the hydrogen bonds between complementary base pairs
• single stranded binding proteins stabilize the unwound parental DNA

Question 9

DNA Replication

Elongation

Answer 9

-RNA primase synthesizes the short RNA stretches of nucleotides which are complementary to the parental strands from which DNA polymerase can then elongate

Question 10

Topoisomerases

Answer 10

-able to bind upstream of the replication fork and minimize the strain that occurs from unwinding

Question 11

DNA Polymerase 2

Answer 11

does most of the elongation work for prokaryotes

Question 12

DNA polymerase 1

Answer 12

responsible for removing the RNA primer after DNA replication and replacing short sequences with DNA nucleotides

Question 13

Proofreading DNA

Answer 13

• errors in the strand can occur so the cell has an innate mechanism
• DNA polymerases are able to proofread each nucleotide as they’re added

Question 14

Telomeres

Answer 14

• regions at ends of linear chromosomes
• mainly made up of repetitions of one short sequence
• serves as a buffer zone so coding genes are protected
• telomeres become shorter during successive rounds

Question 15

Telomerase

Answer 15

• specific type of reverse transcriptase
• able to synthesize DNA from RNA
• binds to tail of telomere and catalyzes the extension of the template by adding more telomere repeats

Question 16

Eukaryotic Origin of Replication

Answer 16

• DNA replication is unable to complete the 5’ ends because its linear
• as a result shorter and shorter DNA molecules are produced with uneven ends