DNA replication

Question 1

When does DNA replication occur in the cell cycle, why does DNA replication occur at this specific stage?

Answer 1

• Before cell division (mitosis/ meiosis.) During interphase.
• DNA must replicate to provide a copy of DNA for the new cell that is created by cell division.

Question 2

What is the method of DNA replication called? What does the daughter DNA from this method of replication compose of?

Answer 2

• “Semi- conservative replication.”
• In the daughter DNA (ie. replicated DNA), one strand is from parental DNA (ie. original copy of DNA) and the other strand is newly synthesised.

() - extra info for clarification.

Question 3

Why is semi- conservative replication of DNA important?

Answer 3

• Ensures genetic continuity between generations of cells (as all of the daughter DNA will have original copy of the initial DNA.)

() - extra info for clarification.

Question 4

Why is complementary base pairing important in DNA replication?

Answer 4

• Enables identical copies of DNA to be created.
• Helps to reduce copying errors (which would result in mutations.)

Question 5

Give the 2 key enzymes that are involved in semi- conservative DNA replication.

Answer 5

1.) DNA helicase
2.) DNA polymerase.

Question 6

What is meant by term “parental DNA?”

Answer 6

• Name given to the original DNA that is going to be copied.

Question 7

What is step 1 of semi- conservative DNA replication?

Answer 7

• DNA helicase breaks hydrogen bonds between the complementary base pairs between the two polynucleotide strands within the double helix.
• This causes the DNA double helix to unwind/ the two strands separate from each other.

Question 8

Step 2 of semi- conservative DNA replication.

Answer 8

• Each of separated parental DNA strands act as a template (for other nucletodies. )
• Free- floating nucleotides - within nucleus- are attracted to their complementary exposed base pairs on the template strands’ (nucleotides) of the parental DNA (POINT: the nucleotide is just NEXT to its complementary base pair, not actually bonded to each other at this point.)

() - extra info for clarification.

Question 9

Step 3 of semi- conservative DNA replication.

Answer 9

• The adjacent nucleotides (one on parental strand/ one on synthesised strand) are joined together to form a phosphodiester bond by a condensation reaction.
• DNA polymerase catalyses the joining together of adjacent nucleotides.

Question 10

What are the 2 sets of daughter DNA (produced from semi- conservative replication) comprised of?

Answer 10

• Contains one strand of parental/ original DNA.
• Contains one newly synthesised strand of DNA.

Question 11

Function of DNA helicase.

Answer 11

• Unwinds double helix DNA and breaks hydrogen bonds between the two polynucleotide strands.

Question 12

Function of DNA polymerase.

Answer 12

• DNA polymerase catalyses the condensation reaction that joins together adjacent nucleotides.

Question 13

What is the role of the template strand (in DNA replication?)

Answer 13

• To determine the order of bases.