Unit 1 Key Area 2

Question 1

What are DNA nucleotides made up of?

Answer 1

Deoxyribose sugar, phosphate, base

Question 2

DNA structure

Answer 2

Consists of two strands of repeating units twisted into a double helix

Question 3

what are the bonds that hold DNA strands together?

Answer 3

Hydrogen bonds

Question 4

Why has DNA got a sugar-phosphate back bone?

Answer 4

Because of the strong chemical bonds forming between the phosphate of one nucleotide and the carbon 3 of the deoxyribose on another nucleotide

Question 5

DNA replication steps

Answer 5

1. DNA is unwound and hydrogen bonds are broken between bases. Forming two template strands.
2. One strand of the replication fork is the template for the leading strand and the other strand is the template for the lagging strand.
3. DNA polymerase can only add DNA nucleotides in one direction meaning that one strand is replicated continuously and the other strand is replicated in fragments.

Question 6

PCR

Answer 6

92-98C- Hydrogen bonds between chains break, separating two strands
50-65C- Allows primers to bind to the target sequence
70-80*C- Heat tolerant DNA polymerase then replicates the target region of DNA

Question 7

3 Medical uses of PCR

Answer 7

• The presence or absence of a particular sequence (called screening)
• A diagnosis of genetic disease status
• Risk of disease onset can be made (risk of mutations and likelihood of disease)

Question 8

2 Forensic uses of PCR

Answer 8

• Paternity suit

- To help solve crimes