ST.2 Replication of DNA H (DNAG)

Question 1

Why do cells need to copy their DNA?

Answer 1

DNA is copied during cell division to ensure that new cells have the same number of chromosomes and to ensure that all cells have the same genes

Question 2

What does the nucleus have to contain for DNA to replicate?

Answer 2

DNA (to act as the template), primers, a supply of the 4 types of nucleotides, DNA polymerase and ligase enzymes, a supply of ATP (chemical energy)

Question 3

Why is DNA a unique molecule?

Answer 3

DNA is a unique molecule because it can control its own replication and reproduce itself

Question 4

Process of replication

Answer 4

• Hydrogen bonds between the bases break, separating the strands
• Free nucleotides start to line up with the complementary nucleotides
• 2 DNA molecules, identical to the parental molecule, have been formed

Question 5

Enzyme control of DNA replication

Answer 5

• The enzyme RNA polymerase controls the formation of the sugar-phosphate bonds when making a new strand
• DNA nucleotides can only be added in one direction onto the 3’ end of a growing DNA strand

Question 6

A leading strand is…..?

Answer 6

A leading strand is replicated continuously

Question 7

A lagging strand is…..?

Answer 7

A lagging strand is replicated in fragments

Question 8

What are fragments of DNA joined together by?

Answer 8

Fragments of DNA are joined together by ligase enzyme

Question 9

Label

Answer 9

Question 10

Label

Answer 10

Question 11

Template strands

Answer 11

Original parent strands of DNA that will be copied during the process of DNA replication

Question 12

Free nucleotides

Answer 12

A supply of nucleotides containing different bases. Attached to the replicating strand by DNA polymerase

Question 13

Primer

Answer 13

A short section of nucleotides that attach to the template strand first, indicates where DNA polymerase should start replicating/adding nucleotides

Question 14

DNA polymerase

Answer 14

An enzyme that adds nucleotides to the replicating strands in a 3’ to 5’ direction ONLY

Question 15

DNA ligase

Answer 15

An enzyme that joins fragments of DNA together

Question 16

DNA polymerase direction rule

Answer 16

DNA polymerase can only add DNA nucleotides in one direction resulting in the leading strand being replicated continuously and the lagging strand replicated in fragments

Question 17

What does DNA polymerase require to start replication?

Answer 17

Primers

Question 18

What happens to DNA prior to cell division?

Answer 18

DNA is replicated by DNA polymerase enzyme prior to cell division

Question 19

What does polymerase chain reaction allow?

Answer 19

PCR allows specific sections of DNA to be amplified over and over again in vitro (in a test tube)

Question 20

What is needed in PCR?

Answer 20

DNA template, DNA polymerase enzyme, primers, supply of nucleotides

Question 21

PCR steps

Answer 21

• The DNA is heated to between 92 - 98 degrees celsius, this causes the DNA strands to separate
• The DNA is cooled to between 50 - 65 degrees celsius for a few seconds, this allows short primers to anneal to the target sequences
• The DNA is heated again to between 70 - 80 degrees celsius for heat tolerant DNA polymerase to replicate the region of DNA

Question 22

How many times is PCR repeated?

Answer 22

30 times