(a)[3]
The diagram shows part of a DNA molecule. Examine the diagram and identify the blocks labelled J, K, L and M as accurately as possible.
(b)[2]
The DNA molecule consists of two polymer strands. What prevents these strands from separating from each other?
(c)[3]
List three ways in which the structures of DNA and RNA differ.
(d)[2]
Outline the different roles of mRNA and tRNA in transcription and translation.