The structure of DNA: including nucleotides | Exit Quiz | Oak National Academy

Which words describe the structure of DNA?

• monomer

• polymer

• double helix

• single strand

Answer explanation

DNA is a polymer with a double helix structure.

DNA is made from single repeating subunits called ...

• bases.

• nuclei.

• nucleotides.

• phosphates.

Answer explanation

Nucleotides are the repeating subunits that make up DNA; DNA is therefore a polymer.

Which of these statements about DNA are true?

• The base A always pairs with G.

• Nucleotides are inverted on one strand of DNA.

• The base C always pairs with G.

• The sugar phosphate backbone includes the base of a nucleotide.

Answer explanation

The four bases are, A, T, C and G. A pairs with T and C pairs with G. There are two strands of DNA; one runs in one direction and the other runs in the opposite direction.

What is complementary base pairing?

• DNA is made from repeating bases.

• DNA has a double helix structure.

• DNA unwinds during interphase.

• Bases only pair in a certain way; A-T and C-G.

Answer explanation

Complementary base pairing is where the bases only pair with one other base: A-T and C-G.

Which of the following statements about copying DNA are true?

• DNA is copied during mitosis.

• The double helix DNA unwinds before copying.

• Each single strand acts as a template.

• Four copies of the same double helix DNA are created.

Answer explanation

DNA is copied during interphase. The double stranded DNA unwinds to form two single strands that each act as a template. Free nucleotides are added, creating two copies of the same double helix DNA.

Use the diagram to match the letter to the correct part of the nucleotide.

• A

• base

• C

• sugar

• B

• phosphate

Answer explanation

The three parts of a nucleotide are: phosphate, sugar and base. The sugar phosphate backbone runs down DNA with bases on the inside.