Why can a human gene work in a bacterium?

The genetic code and the mechanisms of transcription and translation are universal.

DNA made from an mRNA template using reverse transcriptase.

What does reverse transcriptase do?

Makes DNA from an RNA template.

Why is cDNA useful for bacteria?

It has no introns, which bacteria cannot remove.

What does a restriction endonuclease do?

Cuts DNA at a specific recognition sequence.

What is a gene machine?

A device that makes a gene from its base sequence.

What does DNA ligase do?

Joins the sugar-phosphate backbones of DNA fragments.

What happens at 95 °C in PCR?

Hydrogen bonds break and the DNA strands separate.

What happens at about 55 °C in PCR?

Primers anneal to the ends of the target sequence.

What happens at about 72 °C in PCR?

Heat-stable DNA polymerase adds nucleotides to make new strands.

What are promoter and terminator regions for?

Promoter: RNA polymerase binds and starts transcription. Terminator: transcription stops.

What is a marker gene used for?

To detect cells that have taken up the vector.

Recombinant DNA technologyAQA A-Level Biology: Flashcards

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What is recombinant DNA technology?

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What is recombinant DNA technology?: Transfer of fragments of DNA from one organism or species to another.
Why can a human gene work in a bacterium?: The genetic code and the mechanisms of transcription and translation are universal.
What is cDNA?: DNA made from an mRNA template using reverse transcriptase.
What does reverse transcriptase do?: Makes DNA from an RNA template.
Why is cDNA useful for bacteria?: It has no introns, which bacteria cannot remove.
What does a restriction endonuclease do?: Cuts DNA at a specific recognition sequence.
What is a gene machine?: A device that makes a gene from its base sequence.
What does DNA ligase do?: Joins the sugar-phosphate backbones of DNA fragments.
What happens at 95 °C in PCR?: Hydrogen bonds break and the DNA strands separate.
What happens at about 55 °C in PCR?: Primers anneal to the ends of the target sequence.
What happens at about 72 °C in PCR?: Heat-stable DNA polymerase adds nucleotides to make new strands.
How many copies after n PCR cycles from one molecule?: $2^n$ copies.
What are promoter and terminator regions for?: Promoter: RNA polymerase binds and starts transcription. Terminator: transcription stops.
What is a marker gene used for?: To detect cells that have taken up the vector.

Exam questions on Recombinant DNA technology

Beta cells of the human pancreas make large amounts of mRNA for insulin. Researchers want bacteria to make human insulin. Bacterial cells cannot remove introns from RNA. The researchers use mRNA from the beta cells as the starting material to obtain a copy of the insulin gene.
Explain why the human insulin gene can be transcribed and translated to make insulin in the bacterial cell.2 marks
A plasmid vector has a single recognition site for the restriction endonuclease EcoRI, which cuts DNA leaving short single-stranded ends. A fragment of human DNA containing a gene is cut out of a chromosome using the same enzyme and then mixed with the cut plasmids.
Explain why EcoRI cuts DNA only at one specific base sequence.2 marks
A forensic laboratory has only a few molecules of DNA from a crime scene. It uses the polymerase chain reaction (PCR) to make many copies of a short target sequence before analysis. The reaction mixture contains the DNA, primers, free nucleotides and a heat-stable DNA polymerase.
Describe what happens in one cycle of PCR.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).