How are polynucleotide DNA strands held together? (3 marks)

The two antiparallel strands of DNA are held together by hydrogen bonds joining the bases of each complementary nucleotide; Adenine is held to Thymine by 2 hydrogen bonds, and Guanine to Cytosine by 3 hydrogen bonds.

SA

Related Biology A Level answers

All answers ▸

Explain how the sinoatrial node (SAN) ensures that oxygenated blood enters the aorta.


What is saltatory conduction?


What does heat do to an enzyme and why can enzymes not be 'killed'?


What is eutrophication?