HSC Exam Practice

Sample response. A genetic technology is any technology used to analyse, manipulate or direct inheritance and genetic change. It is broader than direct DNA editing — it also includes reproductive technologies (e.g. artificial insemination, artificial pollination), gene cloning, recombinant DNA technology, and whole-organism cloning. The defining feature is that the technology intentionally induces a genetic outcome rather than relying on chance.

Marking notes. 1 mark for identifying genetic technology as analysing / manipulating / directing inheritance; 1 mark for stating it is broader than DNA editing; 1 mark for naming two or more categories of technology covered by the term (reproductive, cloning, recombinant DNA).

Sample response. Artificial insemination is a reproductive technology — it acts at the level of reproduction in animals, controlling which sperm fertilises an egg. It does not insert any new DNA sequence into the genome, so the genetic outcome is a new combination of alleles that already exist in the species. Recombinant DNA technology acts at the level of DNA sequence in cells — it combines selected DNA from different sources and uses a vector to insert it into a host genome. The genetic outcome can be a new sequence that did not previously exist in that species' allele pool, including DNA from another species (a transgenic outcome).

Marking notes. 1 mark — biological level of artificial insemination (reproduction / gamete combination); 1 mark — genetic outcome of artificial insemination (reshuffles existing alleles, no new DNA sequence inserted); 1 mark — biological level of recombinant DNA technology (DNA sequence in cells); 1 mark — genetic outcome of recombinant DNA technology (new sequence introduced, can cross species).

Sample response. A vector is the carrier that physically transports recombinant DNA into a host cell, allowing the chosen sequence to enter, replicate and (often) be expressed. An example is a bacterial plasmid such as pUC19 or pBR322; modified viruses (e.g. lentivirus, AAV) are also commonly used as vectors.

Marking notes. 1 mark for correctly identifying the role of the vector (carrier that delivers DNA into a host cell); 1 mark for naming a valid example (plasmid OR named plasmid OR modified virus / lentivirus / AAV).

Sample response. Although a nuclear clone carries the same nuclear DNA as its donor, the cytoplasm of the egg cell used in somatic-cell nuclear transfer supplies mitochondrial DNA from the egg donor, so the clone's mitochondrial genome may differ. In addition, epigenetic patterns (DNA methylation, histone modifications) are not perfectly reset, and the developmental environment (uterine conditions, post-natal experience) further shapes phenotype. The cloned cats whose coat-pattern differed from the donor despite identical nuclear genomes are a clear lesson example.

Marking notes. 1 mark — identifies mitochondrial DNA from the egg cell as a source of difference; 1 mark — identifies epigenetic patterns / methylation as a source of difference; 1 mark — identifies developmental environment as a source of difference OR cites the cloned cat coat-colour example as evidence.

Sample response. (i) Producing large quantities of a selected DNA sequence for laboratory analysis (e.g. sequencing, restriction mapping, PCR template preparation). (ii) Producing large quantities of a recombinant gene for protein manufacture in bacterial culture (e.g. human insulin production in E. coli). Other accepted answers: preparing DNA for further vector construction; providing template for diagnostic probes; building DNA libraries.

Marking notes. 1 mark per correctly described use that is not "introducing a new trait into a whole organism". Max 2.

Sample response (a). Cleavage efficiency increases sharply across the three technologies — ZFNs achieve ~10%, TALENs ~20% (roughly double the ZFN figure), and CRISPR-Cas9 ~60% (approximately 6× higher than ZFNs and 3× higher than TALENs). The trend mirrors the order in which the technologies were introduced (2003 → 2011 → 2012): the newer technologies are substantially more efficient at the target site.

Sample response (b). All three technologies belong to the DNA-level category of genetic technologies (specifically, DNA editing through targeted double-strand breaks). The size of the difference within this single category means an HSC response that simply says "DNA editing technologies are used to induce genetic change" understates the variation: choice of editing tool determines whether an experiment is feasible in weeks (CRISPR) or months (ZFNs), and whether enough edited cells will be recovered for downstream use. A strong answer therefore names the specific tool (e.g. CRISPR-Cas9) and uses its efficiency / design-time figures rather than treating "DNA editing" as a single undifferentiated technology.

Marking notes. Part (a) — 1 mark for the increasing trend across the three; 1 mark for quoting at least two values from the graph correctly; 1 mark for relating the trend to the order of introduction or for stating an approximate fold-difference (e.g. CRISPR ~6× ZFN). Part (b) — 1 mark for correctly identifying the DNA-level / DNA-editing category; 1 mark for explaining why within-category differences matter for an HSC response; 1 mark for stating that specific named technology + efficiency figure is required rather than treating "DNA editing" as one thing.

Sample response. Current genetic technologies that induce genetic change all give humans more control over genetic outcomes than chance alone, but "control" is not a single thing — what is being controlled depends on the category of technology used, and the value of that control depends on the purpose. Reproductive technologies such as artificial insemination control which gametes combine: a chosen sire can fertilise many cows, spreading selected alleles efficiently without altering DNA sequence. DNA-level technologies such as recombinant DNA technology exert a different kind of control — they can introduce a new sequence (e.g. the cry gene in Bt cotton) that no individual in the species' allele pool previously carried; reproductive crosses alone could never have produced this outcome. Whole-organism cloning (e.g. somatic-cell nuclear transfer) controls a third thing — the preservation of an entire genotype, avoiding the reshuffling that occurs in sexual reproduction. The claim is therefore partly correct: each category demonstrably increases human control on its own axis. However, "control" is limited as an evaluation criterion in three ways. First, control over the genetic outcome does not guarantee control over the phenotypic outcome — a nuclear clone may still differ from its donor because mitochondrial DNA, epigenetic patterns and the developmental environment all influence phenotype. Second, control at one level can introduce problems at another — global adoption of clonal Cavendish bananas gave control over fruit phenotype but reduced genetic variation, leaving the crop vulnerable to Fusarium TR4; similarly, transgenic Bt cotton has been followed by pink-bollworm resistance and secondary-pest outbreaks. Third, "more control" is not the same as "always good" — the value depends on purpose (medical, agricultural, research) and on social context. A defensible judgement therefore is that current genetic technologies do give humans more control over genetic outcomes, and that this is a major advantage, but the kind of control gained and its consequences depend on the technology chosen and the context it is applied in. A Band 6 HSC response uses all three lesson categories together rather than ranking one as universally superior.

Marking notes. 1 mark — defines / applies "current genetic technologies that induce genetic change" and connects the idea to increased human control over genetic outcomes. 1 mark — names a reproductive technology (artificial insemination or artificial pollination) and identifies what it controls (gamete combination, allele combination). 1 mark — names a DNA-level technology (recombinant DNA / gene cloning / CRISPR-Cas9) and identifies what it controls (DNA sequence at a chosen site, ability to introduce a sequence not present in the species). 1 mark — names whole-organism cloning (somatic-cell nuclear transfer) and identifies what it controls (preservation of an entire genotype without meiotic reshuffling). 1 mark — identifies at least one limitation of "control" as a criterion (genotype does not equal phenotype; mitochondrial DNA / epigenetics / developmental environment; resistance evolution; secondary pests; ethical and social context). 1 mark — uses a named real-world example (Cavendish + TR4, Bt cotton + pink bollworm, Casgevy + sickle-cell, cloned cats with different coats) to support the limitation. 1 mark — reaches an explicit evaluative judgement that "control" is a real but partial advantage and that effectiveness depends on technology category + purpose, using all three lesson categories.