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Biotechnology - TCE Biology (Tasmania)

Syllabus dot point

“Demonstrate and apply the use of enzymes to manipulate DNA, including polymerase to synthesise DNA, ligase to join DNA and endonucleases to cut DNA; investigate genome sequencing”

TCEBiologyDNA, genetics and cell division…8 min read

Quick answer

Biotechnology uses tools such as PCR to copy DNA, gel electrophoresis to separate DNA fragments, recombinant DNA technology to transfer genes between organisms, and CRISPR-Cas9 to edit specific sequences. Each has powerful applications and raises ethical and social questions.

What is examined from this page

BIO315124 asks you to apply the use of enzymes to manipulate DNA (DNA polymerase to synthesise DNA, ligase to join DNA and endonucleases to cut DNA) and to investigate genome sequencing, at a general level; this is part of criterion 5. The external assessment specifications exclude recombinant DNA technology, PCR testing and CRISPR from the exam, noting that they can be investigated through criterion 4 (science as a human endeavour), which is assessed by your school. Gel electrophoresis appears in the course as a practical inquiry skill.

What this dot point is asking

Polymerase chain reaction (PCR)

PCR makes millions of copies of a specific DNA sequence from a tiny starting sample. It relies on a heat-stable DNA polymerase (often Taq polymerase) and short single strands called primers that mark the start and end of the target region. The reaction is repeated in cycles of three temperature steps:

  1. Denaturation: heating to around 95 degrees Celsius separates the two DNA strands.
  2. Annealing: cooling to around 55 degrees Celsius lets primers bind to their complementary sequences.
  3. Extension: warming to around 72 degrees Celsius lets polymerase build new strands.

Each cycle doubles the amount of target DNA, so the quantity grows exponentially. PCR is used in disease diagnosis, forensic analysis, and preparing samples for further study.

Recombinant DNA

Recombinant DNA is a single DNA molecule made by joining genetic material from two different sources, for example inserting a human gene into a bacterial plasmid.

Gel electrophoresis

Gel electrophoresis separates DNA fragments by size. DNA is loaded into wells in a gel and an electric current is applied. Because DNA is negatively charged (due to its phosphate groups), it moves towards the positive electrode. Smaller fragments move through the gel mesh faster and travel further, so fragments separate into bands by length. Comparing band patterns underlies DNA profiling, used in forensics and paternity testing, and lets scientists check the size of DNA produced in other procedures.

Recombinant DNA technology

Recombinant DNA technology, or genetic engineering, transfers a gene from one organism into another. A typical workflow:

  1. Restriction enzymes cut DNA at specific recognition sequences, often leaving sticky ends.
  2. The same enzyme cuts a vector, usually a bacterial plasmid, leaving matching sticky ends.
  3. The gene and plasmid are joined by the enzyme DNA ligase, forming recombinant DNA.
  4. The plasmid is taken up by a host cell (transformation), which then expresses the gene.

This technology is used to produce human insulin in bacteria, to make genetically modified crops with pest resistance, and to manufacture vaccines and other proteins.

Producing human insulin

The human insulin gene is cut out using a restriction enzyme. A bacterial plasmid is cut with the same enzyme so the sticky ends match. DNA ligase seals the insulin gene into the plasmid, and the recombinant plasmid is inserted into bacteria. The bacteria multiply rapidly, each copy expressing the gene, so a large culture produces human insulin that can be purified for people with diabetes.

CRISPR-Cas9 gene editing

CRISPR-Cas9 allows precise editing of a specific DNA sequence. A short guide RNA is designed to match the target sequence and directs the Cas9 enzyme to that exact location, where Cas9 cuts both strands of the DNA. The cell then repairs the cut, and during repair scientists can disable a gene or insert a new sequence. CRISPR is faster, cheaper, and more precise than older methods, with potential applications in treating genetic diseases, improving crops, and research.

Precision is the key advantage

The power of CRISPR-Cas9 comes from the guide RNA, which targets one specific sequence. This lets researchers edit a chosen gene rather than relying on the random insertion typical of earlier genetic engineering.

Applications and implications

Biotechnology brings major benefits: better medicines, faster diagnosis, higher-yielding and more resilient crops, and powerful research tools. It also raises ethical, social, and ecological concerns that you should be able to discuss:

  • Safety and unintended effects of genetically modified organisms in the environment.
  • Access and equity, since advanced treatments can be expensive.
  • Consent and privacy around genetic information.
  • The ethics of editing human embryos (germline editing), which would affect future generations.

A balanced evaluation weighs the likely benefits against the risks and uncertainties, and recognises that regulation and informed public debate guide how these tools are used.

Treating GM and gene editing as the same

Traditional recombinant DNA technology usually inserts a foreign gene at a random position, often from a different species. CRISPR-Cas9 edits a precise, chosen location and can change an organism's own genes without adding foreign DNA. Do not describe them as identical processes in an exam answer.

Exam-style questions

Questions in the style of TASC exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.

Original7 marks
A forensic scientist has a tiny DNA sample from a crime scene. Describe how PCR could be used to amplify the sample, naming the three temperature steps of one cycle and what happens at each, and explain how gel electrophoresis could then be used to compare the sample with DNA from a suspect.
Show worked answer →

A 7 mark answer covers the three PCR steps and the electrophoresis comparison.

PCR step 1 - denaturation (about 95∘C95^{\circ}C)
The sample is heated so the hydrogen bonds break and the double-stranded DNA separates into two single strands.
PCR step 2 - annealing (about 55∘C55^{\circ}C)
The mixture is cooled so primers bind to complementary sequences at the ends of the target region.
PCR step 3 - extension (about 72∘C72^{\circ}C)
Heat-stable DNA polymerase (Taq) adds free nucleotides to extend new complementary strands. Repeating the cycle doubles the DNA each time, giving millions of copies.
Gel electrophoresis
The amplified DNA is cut with restriction enzymes and loaded into wells in a gel. An electric current moves the negatively charged fragments toward the positive electrode; smaller fragments travel further, separating them into a banding pattern. If the crime-scene banding pattern matches the suspect's pattern, it supports a match.

Markers reward all three correctly named PCR steps with temperatures/events and a correct account of size-based separation in electrophoresis.

Original6 marks
Describe how a gene of interest can be inserted into a bacterial plasmid to produce recombinant DNA, naming the enzymes used, and outline one ethical implication of using genetically modified organisms.
Show worked answer →

A 6 mark answer covers the recombinant steps with enzymes plus a reasoned ethical point.

Cutting
The same restriction enzyme cuts both the gene of interest and the plasmid, leaving complementary sticky ends so they can join.
Joining
The gene is mixed with the cut plasmid; DNA ligase forms bonds that seal the gene into the plasmid, creating recombinant DNA.
Insertion and expression
The recombinant plasmid is taken up by a bacterium (transformation), which then transcribes and translates the gene to make the desired protein (for example human insulin) as it reproduces.
Ethical implication
Any one reasoned point, for example: concerns about unknown long-term ecological effects if GM organisms escape and cross with wild populations, or questions about safety, labelling and corporate control of patented organisms.

Markers reward restriction enzyme and ligase named in the correct roles, the transformation step, and one clearly reasoned ethical implication.

Practise this

Sources & how we know this

Based on the official TASC course document. Not yet individually reviewed by a person; always check TASC and your school's materials for current rules.

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