3.4 DNA Replication

Question 1

Outline the unwinding of the double helix

Answer 1

Initiated by the enzyme helicase. Breaks hydrogen bonds between base pairs. DNA is separated into two separate strands; nitrogenous bases exposed.

Question 2

Outline the formation of the two identical complementary strands

Answer 2

There are free floating nucleotides in the nucleoplasm, which locate base pairs on parent strand. Hydrogen bonds formed between bases, then nucleotides bonded together covalently by enzyme DNA polymerase. Other strand formed in similar fashion, but opposite direction (anti-parallel).

Question 3

Explain the significance of complementary base pairing in the conservation of the base sequence of DNA.

Answer 3

The two DNA molecules formed will be identical to the original molecule. The parent strand acts as a template.

Question 4

Explain that DNA replication is semi-conservative.

Answer 4

“Semi-conservative” because half of preexisting DNA molecule is always conserved. DNA molecules are never completely new: one strand will be from the original molecule, one strand will be newly synthesized.

Question 5

Contrast between the leading and lagging strand

Answer 5

On the leading strand, the DNA polymerase travels the same direction as the Helicase. On the lagging strand, the DNA polymerase travels in the opposite direction, and therefore must work in smaller sections.