The structure of DNA | Exit Quiz | Oak National Academy

In plant and animal cells, the genome is stored in the ...

Answer explanation

In plants and animals, or any eukaryotic cell, the chromosomes are all stored in the nucleus of the cell and are too big to leave it.

DNA is a nucleic acid polymer. How many nucleic acid strands make up each DNA molecule?

• one

• two

• four

• eight

Answer explanation

Each DNA molecule has two strands. The bases of each nucleotide hold the two strands together.

Put these in size order, starting with the smallest.

• nucleus

• nucleotide

• DNA molecule

• nucleic acid

Answer explanation

Nucleic acids are polymers made from many nucleotides. Each DNA molecule has two nucleic acid strands held together by the bases on each of the strands and twisted into a double helix.

The photograph shows a model of part of a DNA molecule. It is made from liquorice and jelly babies. What would improve the model?

• Add more than four colours of jelly baby.

• Add more than two liquorice sticks.

• Twist the model to form a helix.

• Bend the model into a square.

Answer explanation

A DNA molecule is often described as a double helix. It has two nucleic acid chains held together by nucleotides, a bit like the rungs of a ladder, which are twisted to form a double helix shape.

Scientists often use models such as the DNA models you have studied. Why?

• Models are exact copies of things such as DNA.

• Models always contain a lot of details.

• Models are always much larger than the things they represent.

• Models help to explain things that are difficult to see or understand.

Answer explanation

Models are simpler than the real things they represent. They allow us to focus on important aspects of the things in a way we can visualise and so understand better.

Match the word to its meaning.

• polymer

• a chemical made from many smaller chemical groups

• DNA

• the building blocks for nucleic acids and DNA

• nucleotide

• a polymer made of four nucleotides, which make up the genetic code

• nucleic acid

• a polymer made up of nucleotides, an example is DNA

Answer explanation

Many nucleotides join together to make a nucleic acid strand. Nucleic acid is therefore a polymer. Two nucleic acid strands join together to make a DNA molecule. DNA is also a polymer.