HKS
Preface: The question talks about insulin gene cloning in 2020, meaning you would clone the whole insulin gene at once. If it talks about how they would do it in the 1980s (unlikely) you would have the say they cloned the insulin A and insulin B chain separately.
Not going to admit, this question is a bit rubbish as they say 'cloned and expressed' in bacteria, but the examiners report only talks about cloning the insulin gene. Nowhere does it talk about the insulin gene being expressed.
I'd personally write the whole process out as I wouldn't want to risk the marks.
But, if I were to attempt to condense this information, I'd write the following:.
Reverse transcriptase synthesises synthetic cDNA molecule of insulin with no introns.
Restriction endonuclease cut sticky ends upstream and downstream insulin gene and same endonuclease cut sticky ends on plasmid.
Insulin gene mixed with plasmid, complementary overhangs means insulin gene may anneal to plasmid. DNA ligase repairs phosphodiester bonds along sugar phosphate backbone.
Plasmids are delivered into bacteria.
Bacteria are grown on antibiotics, and bacteria with recombinant plasmid are identified.
Bacteria transcribe and translate insulin gene, producing insulin protein.
Insulin protein is isolated from bacteria.
(this is still long sorry)
If you have time, try write the whole process, if you are familiar with it, on the extended response page. But honestly, I think this question is incredibly poorly worded, the examiners report does not even answer their question.
