54 WJEC Biology AS Level - Study And Revision Guide - Neil Roberts (1.5 Nucleic Acids And Their Functions)

Question 1

What are the functions of DNA in organisms?

Answer 1

DNA has two main functions in organisms:

1. Protein synthesis
2. Replication

Question 2

Describe the DNA function of protein synthesis.

Answer 2

The sequence of bases in one strand, called the template strand, determines the order of amino acids in the polypeptide (primary structure).

Question 3

Describe the DNA function of replication.

Answer 3

When cells divide, a complete copy of the DNA in the cell needs to be made.

Both DNA strands separate, and each strand acts as a template to synthesise a complementary strand.

Question 4

What are the theories for how DNA replicates?

Answer 4

Three theories for how DNA replicates have been proposed:

1. Conservative replication
2. Semi-conservative replication
3. Dispersive

Question 5

Describe the theory of conservative replication of DNA.

Answer 5

Original parent double-stranded molecule is conserved, and a new double-stranded DNA molecule synthesised from it.

Question 6

Describe the theory of semi-conservative replication of DNA.

Answer 6

Parental strands separate, and each strand acts as a template to synthesise a new strand.

The new molecule consists of one original parent strand and one newly synthesised strand.

Question 7

Describe the theory of dispersive replication of DNA.

Answer 7

The newly synthesised molecules contain fragments from the original parent strand and newly synthesised DNA.

Question 8

Draw the structure of tRNA.

Answer 8

Question 9

Draw a diagram of the DNA replication theories

Answer 9