Haemoglobin is a protein in red blood cells.
The Table shows some mRNA codons and the amino acids they code for.
Table
| mRNA codon | Amino acid |
|---|---|
| GAG | glutamic acid |
| GUG | valine |
| CUC | leucine |
| CAC | histidine |
In one gene for haemoglobin, the DNA strand used to make mRNA contains the triplet CTC.
In people with sickle cell disease, this triplet has changed to CAC.
Give the mRNA codon produced from the triplet CAC.
Use the Table to name the amino acid coded for by the triplet CAC in the DNA.
In sickle cell disease, the haemoglobin molecules stick together. This makes the red blood cells change shape.
Explain how a change of one base in the coding DNA can change the properties of haemoglobin.
44 exam-style questions on Edexcel GCSE Biology 3.2 DNA and protein synthesis, covering 3.2.1 DNA structure as a polymer, 3.2.2 Genome and gene definitions, 3.2.3 Extracting DNA from fruit, 3.2.4 Base order determines protein shape, 3.2.5 Stages of protein synthesis, 3.2.6 Non-coding DNA variants affecting phenotype, and 3.2.7 Coding DNA variants affecting phenotype. Each one has a worked solution and a mark scheme showing where the marks go.