Interferon-alpha (IFN-α) may be manufactured as a recombinant human protein to treat certain cancers. The IFNA2 gene codes for IFN-α. One way to make recombinant IFN-α is to use genetically engineered Escherichia coli bacteria carrying recombinant plasmids. Each recombinant plasmid includes the IFNA2 gene; three lac operon regulatory sequences (promoter, operator and lacI); and an antibiotic resistance gene, AMPR. The sequences for the lacI gene and AMPR gene each have their own promoter. Therefore, these genes are always expressed in E. coli bacteria that contain this recombinant plasmid. Fig. 2.1 shows the recombinant plasmid. The promoter regions of the lacI gene and AMPR gene are not shown.
(a(i))[2]
Explain the function of the gene lacI in controlling transcription of the IFNA2 gene from 0 hours to 4 hours.
(a(ii))[3]
With reference to Fig. 2.2, describe the changes in the concentration of recombinant IFN-α in the culture containing IPTG from the time IPTG was added at 4 hours until the end of the experiment at 28 hours.
(a(iii))[1]
Suggest one reason for the difference between the concentration of recombinant IFN-α in the culture at 8 hours in the presence of lactose and the concentration of recombinant IFN-α in the culture at 8 hours in the presence of IPTG.
(a(iv))[1]
Suggest one reason for the change in the concentration of recombinant IFN-α in the culture containing IPTG from 12 hours to 16 hours.
(b)[1]
The gene AMPR in the plasmid shown in Fig. 2.1 codes for a protein that gives resistance to the antibiotic ampicillin. Suggest how AMPR enables genetically engineered E. coli containing the recombinant plasmid to be identified.
(c)[5]
Bacteria can evolve antibiotic resistance by natural processes. Outline how bacteria can evolve to become resistant to antibiotics.
Worked solution & mark scheme
This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: “R is a regulatory gene that codes for a repressor protein / transcription factor” …