DNA Replication

Question 1

Semi-conservative replication

Answer 1

Two parental strands separate and each serves as a template for a new progeny strand

Correct theory

Question 2

Conservative replication

Answer 2

Two parental strands stay together and somehow produce another daughter helix and completely new strands

Incorrect theory

Question 3

Dispersive replication

Answer 3

DNA becomes fragmented so that new and old DNA coexist in the same strand a after replication

Incorrect theory

Question 4

DNA helicase

Answer 4

Enzyme that breaks hydrogen bonds between complimentary base pairs (strands unzipped)

Question 5

Single stranded binding proteins (SSBS)

Answer 5

Bind to exposed strands, preventing them from rejoining (annealing?)

Question 6

Why does DNA need to be replaced?

Answer 6

Growth
Repair
Reproduction

Question 7

DNA gyrase

Answer 7

In bacteria, it relieves tension by cutting and re annealing the two strands

Question 8

Topoisomerase

Answer 8

In eukaryotic cells relieves tension between two strands of the DNA

Question 9

DNA polymerase lll

Answer 9

Adds complementary nucleotides in the 5’ to 3’ direction using RNA primers as starting points

Question 10

RNA primers

Answer 10

Short segments of RNA that provides a starting point for DNA nucleotides to attach to

Question 11

Primase

Answer 11

The enzyme required to add RNA primers

Question 12

Okazaki fragments

Answer 12

Lagging strand is discontinuous in short fragments away from fork

Question 13

DNA polymerase l

Answer 13

Removes RNA primers and replaces them with correct DNA nucleotides

Question 14

DNA ligase

Answer 14

Joins Okazaki fragments together by making a phosphodiester bond

Question 15

DNA polymerase l & lll

Answer 15

Are the proofreaders of new daughter DNA

Question 16

Stage one of DNA replication

Answer 16

1. DNA helicase
2. SSBS
3. Topoisonerase relieves tension
4. Sections of DNA are replicated as soon as it unwinds
5. Replication forks
6. Two daughter DNA molecules formed

Question 17

Replication forks

Answer 17

• Junction where DNA is still joined and enzymes are bound
• several forks found on one DNA molecule to increase speed of replication
• replicating bubbles form and meet creating daughter DNA molecules

Question 18

Priming

Answer 18

• DNA polymerase cannot start incorporating nucleotides on its own
• needs help from RNA polymerase lll

Question 19

Stage two of DNA replication

Answer 19

• Elongation
• Direction of replication occurs in the 5’ to 3’ direction
• bidirectional (occurs toward fork on one strand and away from fork on the other strand)
• leading strand (built continuously towards fork 5’ to 3’)
• lagging strand (discontinuously in shirk fragments)

Question 20

Stage 3 of DNA replication

Answer 20

• quality control
• DNA polymerase l and lll are the proof readers of new daughter cells
• when they encounter a mistake in the sequence they act as an exonuclease and cut out the wrong nucleotide and replace with correct one
• the process happens immediately