DNA Replication

Question 1

Meselson and Stahl big idea

Answer 1

DNA undergoes semiconservative replication

Question 2

What does semiconservative replication mean?

Answer 2

DNA opens gets copied and a new strand bonds with an old strand

Question 3

Step 1 of DNA Replication

Answer 3

DNA must unwind to expose a single stranded template

Question 4

What enzymes do step 1 of DNA replication use?

Answer 4

• Helicase
• Topoisomerases (Gyrase)

Question 5

What does helicase do?

Answer 5

• Unzips and unwinds the double helix
• Breaks hydrogen bonds

Question 6

What does topoisomerase (gyrase) do?

Answer 6

• Detangler
• Prevents supercoils by nicking and resealing DNA

Question 7

Step 2 of DNA Replication

Answer 7

DNA must be held open, not to reform a coil

Question 8

What do Single Stranded Binding Proteins do?

Answer 8

• Bind to the uncoiled DNA and keep it open

Question 9

Step 3 of DNA Replication

Answer 9

A primer must be created before DNA synthesis can occur

Question 10

What is primer?

Answer 10

• Short sequence of RNA, complementary to template
• 3’ end where DNA synthesis can begin

Question 11

What is primase?

Answer 11

Enzyme that synthesizes RNA primer

Question 12

What is RNA polymerase?

Answer 12

Synthesizes primers on leading strand

Question 13

Note about primase

Answer 13

Primase is a type of RNA polymerase

Question 14

Leading strand

Answer 14

• New strand that is synthesized continuously
• Synthesized towards replication fork

Question 15

Lagging Strand

Answer 15

• Synthesized in short fragments called Okazaki fragments which are later joined together
• Discontinuously
• Synthesized away from replication fork

Question 16

Step 4 of DNA Replication

Answer 16

DNA synthesis begins

Question 17

What is DNA polymerase 3

Answer 17

• Enzyme that catalyzes the addition of nucleotides complementary to the template strand

Question 18

What is a nucleoside triphosphate

Answer 18

• Free floating nucleotides with extra phosphate for energy
• Each nucleotide that is added to a growing DNA strand is a nucleoside triphosphate

Question 19

What does the phosphate in a nucleoside triphosphate do?

Answer 19

• The phosphate provides energy needed to drive the reaction that makes phosphodiester bonds

Question 20

What direction does DNA synthesis occur in?

Answer 20

5’ to 3’ direction

Question 21

DNA polymerase 1, first function

Answer 21

• Edits mistakes
• Proofreads chain
• Exonuclease activity

Question 22

Step 5 of DNA Replication

Answer 22

Synthesis of DNA occurs on both template strands

Question 23

Step 6 of DNA Replication

Answer 23

RNA primers are removed

Question 24

DNA polymerase 1, second function

Answer 24

• chews up RNA primers and replaces them with DNA nucleotides
• All primers are removed

Question 25

What is Nick Translation?

Answer 25

When primers are replaced by DNA nucleotides

Question 26

Step 7 of DNA Replication

Answer 26

All nicks are repaired

Question 27

What is DNA Ligase

Answer 27

• Acts like glue to make phosphodiester linkages
• Seals the nicks between Okazaki fragments