The genetic code | Starter Quiz | Oak National Academy

Starting with the largest, put the structures in order of decreasing size.

• cell

• genome

• gene

• chromosome

• nucleus

Answer explanation

This is the correct order of size for eukaryotic cells (animal, plant and fungal cells). Prokaryotic (e.g. bacterial cells) do not have a nucleus and have one chromosome made of a single DNA molecule.

What does the order of nucleotide bases in a gene determine?

• the structure of a carbohydrate molecule

• the structure of a fat molecule

• the structure of the nucleus

• the structure of a protein molecule

Answer explanation

A gene carries the instructions to build a protein.

What is the name of the type of molecule that acts as a catalyst in living organisms?

(a)  

Answer explanation

Without enzymes, chemical reactions would be too slow to sustain life.

The diagram shows a single nucleotide. Which part of the nucleotide joins the two strands of a DNA molecule together?

(a)  

Answer explanation

Bases pair up across the two nucleic acid strands to form the ‘rungs’ of the DNA ‘ladder’.

One strand of a DNA molecule has the base sequence A A T C G A G C A. Which is the complementary base sequence on the other strand of the DNA molecule?

• A A T C G A G C A

• A C G A G C T A A

• T T A G C T C G T

• C C G A T C T A G

Answer explanation

The complementary base sequence on the other strand of the DNA molecule is T T A G C T C G T.

The photograph shows a model of DNA made from jelly babies and liquorice sticks. In this model, which parts of the nucleotide molecules are represented by the liquorice sticks?

• Bases only

• Sugars only

• Bases and sugars

• Bases and phosphates

• Sugars and phosphates

Answer explanation

The liquorice sticks represent the sugar and phosphate of each nucleotide, which form a long ‘backbone’ of alternating sugar and phosphate units.