Protein synthesis, the genetic code and gene mutationsEdexcel A-Level Biology B: Mind map

Exam questions on Protein synthesis, the genetic code and gene mutations

1. A short section of the anti-sense (template) strand of a gene has the base sequence TAC GGA CTT. This section is transcribed in the nucleus of a cell and the mRNA produced is translated at a ribosome.
   State the anticodon of the tRNA that binds to the first codon of the mRNA and explain how the tRNA ensures the correct amino acid is added.2 marks
2. A patient has a genetic condition caused by a gene mutation within the coding region of a gene. Sequencing shows that a single nucleotide has been deleted close to the start of the coding region of the gene.
   Explain why the deletion is likely to have a more serious effect on the protein than a substitution of one base would.2 marks
3. Sickle cell anaemia is caused by a mutation in the gene for the β-globin polypeptide of haemoglobin. In the normal allele a triplet on the sense strand of the DNA is GAG, which codes for the amino acid glutamic acid. In the sickle cell allele this triplet is GTG, which codes for the amino acid valine.
   Explain how this mutation leads to the production of a different haemoglobin protein.3 marks