Cambridge International A Level Biology Revision Guide

Cambridge International AS Level Biology
4 Look at the structures of nucleotides in Figure 6.2 (page 112). Draw a nucleotide that could be found:
a in either DNA or RNA [1]
b only in DNA [1]
c only in RNA. [1]
[Total: 3]
5 Distinguish between a nucleotide and a nucleic acid. [2]
6 Copy the drawing and annotate it to explain the replication of DNA.
7 Use Appendix 2 (page 513) to find the sequence of amino acids that is coded by the following length of
messenger RNA (mRNA):
AUGUUUCUUGAUUAA [2]
[4]
124
8 The table shows all the messenger RNA (mRNA) codons for the amino acid leucine.
Copy the table and write in, for each codon, the transfer RNA (tRNA) anticodon that would bind with it and the
DNA triplet from which it was transcribed.
mRNA codon tRNA anticodon DNA triplet from which mRNA was transcribed
UUA
UUG
CUU
CUC
CUA
CUG
[6]
9 In most people, the first six amino acids in their β-globin polypeptide chains are:
1 2 3 4 5 6
Val–His–Leu–Thr–Pro–Glu–rest of chain
The DNA triplet coding for the sixth amino acid (Glu) in most people is CTT. In some people this
DNA triplet is CAT.
a What type of mutation is the change from CTT to CAT? [1]
b Use Appendix 2 (page 513) to identify the amino acid in the β-globin polypeptide chains
of people with this mutation. [1]
c State the consequences for a person of having two copies of the mutated gene. [1]
[Total: 3]