Replication of DNA

Question 1

At the end of mitosis, what does each new cell have in terms of chromosomes?

Answer 1

each new cell has single-stranded chromosomes

Question 2

Before a cell can divide again, what must it first do?

Answer 2

It must produce an exact copy of its DNA.
This means that the single-stranded chromosome must become double-stranded chromosomes

Question 3

What is the process of DNA replication?

Answer 3

Before a cell can divide again it must first make an exact copy of its DNA.
This means that the single-stranded chromosome must become double-stranded chromosomes

Question 4

When in the cell cycle does DNA replication take place?

Answer 4

interphase

Question 5

How many steps are involved in DNA replication?

Answer 5

5

Question 6

Explain the first step of DNA replication (1)

Answer 6

The double helix unwinds or uncoils

Question 7

Explain the 2nd step of DNA replication (2)

Answer 7

1. An enzyme breaks the bonds between the base pairs.
2. The 2 strands of the original double helix separate.

Question 8

What causes the breaking of the bonds between base pairs in DNA replication?

Answer 8

enzymes

Question 9

Explain the 3rd step of DNA replication (2)

Answer 9

1. DNA bases that are normally present in the cytoplasm enter the nucleus.
2. The incoming bases attach to the exposed complementary bases (i.e. base pairing occurs)

Question 10

What happens once the DNA strands separate from each other?

Answer 10

DNA bases that are normally present in the cytoplasm enter the nucleus.

Question 11

When the DNA bases enter the nucleus, what to they do?

Answer 11

The incoming bases attach to the exposed complementary bases (i.e. base pairing occurs)

Question 12

Explain the 4th step of DNA replication (1)

Answer 12

In this way, each side of the DNA molecule acts as a mould or template for the new DNA that is formed.

Question 13

Explain the 5th step of DNA replication (2)

Answer 13

1. Each new double strand rewinds to form a double helix.
2. Note that each new DNA double helix is:
   - Half new and half original DNA
   - Identical to the original DNA double helix and to the other new double helix formed.

Question 14

In the two new double helixes produced, what must be noted about them? (2)

Answer 14

Each new DNA double helix is:
- Half new and half original DNA
- Identical to the original DNA double helix and to the other new double helix formed.