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Want to see how you went in the 2024 Biology HSC exam? Read on for the 2024 Biology HSC exam answers!
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The Matrix Biology team is thrilled to publish the 2024 HSC Biology Exam Solutions. These are the answers for the 2024 HSC Biology exam which can be viewed here.
Keep in mind that these answers were not written under exam conditions and may be longer than required.
| Question | Answer | Solution |
| 1 | C | Prions are composed of a single-folded protein. |
| 2 | B | The use of living things for human gain is classed as biotechnology. |
| 3 | B | The genes CDE have been copied twice (duplicated). |
| 4 | D | Ribose and uracil are found in RNA not DNA. |
| 5 | A | The diagram illustrates budding in yeast (a type of fungus). |
| 6 | B | Eggs are haploid gametes that will have half (4) the normal number of chromosomes found in the body cell (8). |
| 7 | A | Stomata will close when it is hot, windy or dry since these conditions will speed up transpiration and water loss. |
| 8 | C | The trypanosomes are the pathogens that are transmitted to the host via the fly vector. Vector transmission is a form of indirect transmission. |
| 9 | C | Only a mutation on the gene for eye colour can produce a new allele for eye colour. |
| 10 | A | The sealed jar is the control which improves the validity of the experiment. |
| 11 | C | Option C was the only one that matched the data presented. |
| 12 | C | The correct order of steps in Koch’s postulates is 4, 2, 1, 3. |
| 13 | D | Plants cannot produce phagocytes or antihistamines. Increased number of stomata is not a defence against pathogens. |
| 14 | A | The cell doubles the amount of DNA during M, then divides once via mitosis during O to end up with the same amount of DNA it started with. |
| 15 | A | Strategies in May-June should focus on preventing entry of the disease into the country. Strategies in July should focus on preventing spread between people. |
| 16 | B | A diverging (concave) lens can be used in front of the eye to extend the focal length so that the focal point is on the retina. |
| 17 | D | If people are living longer with the disease this will increase the prevalence of the disease. |
| 18 | B | Since the population is isolated gene flow cannot occur. B is the correct definition of genetic drift. |
| 19 | D | The same restriction enzyme can be used so that the plasmid and human gene have complementary sequences at their ends. |
| 20 | C | 1 has two affected parents with an unaffected offspring so it must be dominant, since an affected father has not passed the condition on to the daughter it must not be sex-linked. 3 has a condition passed from a father to all daughters but no sons so is sex-linked dominant. |
Pollen is found within the anther, and ovules (eggs) are found within the ovary.
Sexual reproduction produces genetic variability but asexual reproduction does not. Sexual reproduction requires 2 parents while asexual reproduction requires 1.
Sexual reproduction is used by mammals such as humans, while asexual reproduction is used by bacteria, protists and invertebrates such as flatworms (among other examples).
Once they are inoculated, the agar plates are sealed with sticky tape and never opened again. This is to prevent contact or inhalation with pathogenic microbes that may grow on the culture media.
The student could repeat the experiment multiple times to see whether the results are consistent within a margin of error.
Gamma radiation is a form of electromagnetic radiation that is strong enough to pass through the body and damage DNA within the sex cells or gametes within the testes or ovaries.
If not repaired, this DNA damage becomes a germline mutation that can be passed on to offspring.
Lead poisoning is a disease caused by exposure to lead in the environment. It is typically caused by inhalation of dust containing lead or in some cases contaminated food or water.
An education program could be used to decrease the incidence of lead poisoning by raising awareness. Information could include the symptoms of lead poisoning, such as a blue line along the gums and neurological symptoms. It should also include information on sources of lead such as lead paint or lead pipes.
It should include information on the long-term negative impacts of lead exposure in children such as reduced IQ and behavioural problems. This should change individual
behaviour by decreasing exposure to lead and seeking early treatment.
The cloned dog is a genetic clone so it will have all of the genetic instructions that Jack had before he lost his eye. Phenotypic changes such as injury or eye loss are not passed on genetically.
A somatic cell is taken from the animal to be cloned and an egg is harvested from the ovary of a donor animal. The egg cell is enucleated and the nucleus from the somatic cell is extracted and injected into the egg.
The egg is now diploid and has all the genetic material necessary for development into an embryo. The embryo is implanted into a surrogate and the resulting offspring will be a genetic clone of the somatic cell donor.
Red rust disease is a fungal disease that affects wheat production. The fungus spreads via spores carried by the wind. The spores attach to a new plant and grow long, thin hyphae down into the plant tissue through the stomata.
The hyphae then extract nutrients from the plant cells. Infection causes weak plants with poor root development. Severe infections can decrease wheat yield by more than 80%.
Between 1900 and 1945 disease outbreaks due to raw milk were common with at least 10 outbreaks per year. After 1915 when there was a peak of 68 outbreaks, disease outbreaks related to raw milk declined. Outbreaks became rare as pasteurised milk use became more common, there have been less than 5 outbreaks per year due to raw milk since 1950.
Outbreaks caused by pasteurised milk still occur, this may be due to quality control issues with the pasteurisation process or pathogens that are resistant to the heat treatment process. Pasteur used his swan neck flask experiment to disprove spontaneous generation
and support germ theory – the idea that disease is caused by microbes in the environment.
Pasteur also found that heat could kill microbes in beer or wine. Thus, Pasteur’s work eventually led to the pasteurisation process, where raw milk is heated to kill microbes that could cause disease if consumed, e.g., Listeria or Tuberculosis.
The parents are both heterozygous so the cross will be Rr x Rr. Regardless of the genotype of the first child, each subsequent child has a 25% chance of having an affected child with the recessive phenotype rr (see punnet square).
| R | r | |
| R | R R | Rr |
| r | Rr | rr |
Initially, there are two consecutive codons AUC and UUU coding for two amino acids: Isoleucine and Phenylalanine respectively. The deletion of three nucleotides deletes parts of these two different codons.
As a result the first two bases of the first codon ‘AU’ get combined with the last base of the second codon ‘U’ to form a new codon ‘AUU’ which still codes for the amino acid Isoleucine. Therefore, only the Phenylalanine amino acid is lost from the sequence.
A physiological adaptation of endotherms includes altering the metabolic heat production in order to maintain a stable temperature of 37 degrees Celsius. If the body temperature moves below this in mammals, it will cause vasoconstriction and shivering, if the temperature moves above this, it will cause vasodilation and sweating.
7% of 9 Billion people: 0.07 x 9 000 000 000 = 630 000 000 people
Process A is the process of transcription. While the DNA is unwound by helicase in DNA replication, here it is unwound by RNA polymerase. RNA polymerase will add complimentary RNA nucleotides (A, U, C, G), while in DNA replication DNA polymerase will add complimentary DNA nucleotides (A, T, C, G).
The end product of transcription will be a single-stranded RNA molecule, while the end product of DNA replication is two double-stranded DNA molecules. (Could be presented as a table)
Messenger RNA (mRNA) is synthesised during transcription. It is a copy of a gene that can leave the nucleus and be read by a ribosome. mRNA is important to polypeptide synthesis since the sequence of codons on the mRNA will determine the sequence of amino acids in the resulting polypeptide.
During transcription transfer, RNA (tRNA) molecules that have matching anticodons to the codons on the mRNA will deliver a specific amino acid to the ribosome. The tRNA ensure that the correct sequence of amino acids is delivered to the ribosome.
Any mistakes on the mRNA or incorrect amino acids delivered by the tRNA will change the amino acid sequence of the polypeptide and could change the structure and function of the final protein as a result. Changes to protein structure can affect cell function.
4 am.
The human does not experience torpor since their body temperature only decreases by around 1 degree Celsius. The dramatic decline in the kookaburra’s body temperature between 5 pm and 4 am indicates that it was experiencing torpor during this time.
Shivering could increase the body temperature during the inactive period. Shivering causes contraction of skeletal muscles which generates metabolic heat and increases body temperature.
As part of the innate response, the presence of helicobacter is detected by mast cells which release histamine to start the inflammation response. Histamine triggers the nearby blood vessels to dilate, which increases blood flow to the area. It also causes the blood vessels to become ‘leaky’ so that plasma fluid and phagocytes can leave the bloodstream and enter the site of infection.
Phagocytes are white blood cells that engulf the bacteria and use lysozyme enzymes to break them down within a lysosome. They will then excrete any waste material.
As part of the adaptive immune response, some phagocytes will present antigen fragments from the bacteria to T helper cells. These cells will then use chemical signals to activate other immune cells such as B cells. Activated B cells will begin cloning themselves, with the majority of the clones becoming plasma cells that will produce antibodies. Antibodies are tiny proteins that will bind to specific antigens on the surface of the bacteria to disable them and flag them for destruction by the phagocytes.
Memory B and T cells will also be produced. These lay dormant within the lymph nodes, but will be activated if there is a future Helicobacter infection.
Crossing over increases genetic diversity in Jack Jumper ants by producing new combinations of maternal and paternal alleles in the gametes and in the offspring as a result.
Crossing over at the position shown will result in four cells with one chromosome each, with the following combinations of alleles: (DEH)(Deh)(deH)(deh).
Transgenesis is a biotechnology that produces living things with a gene that has been transferred from a different species. This biotechnology has had a significant impact on society as it has provided a reliable supply of therapeutic proteins such as insulin, by inserting human genes into the genomes of bacteria or animals. Since a human gene is used, the product is identical to the human protein.
Transgenesis has also produced crops such as Bt corn that can produce a toxin so that they are pest resistant. This results in greater productivity and food security as there is less crop loss and less pesticide needed.
However there are ethical implications of producing organisms that could decrease species diversity through competition or have unforeseen impacts on the environment. In the case of transgenic animals, they may suffer as a result of their transgenes or the processes used to obtain products from them.
Whole organism cloning is another biotechnology that has benefitted society by producing genetically identical food crops that grow consistently and are all ready to harvest at the same time. It can also be used to clone animals that have useful characteristics such as high milk yield.
However, since whole-organism cloning produces genetically identical copies of a plant or animal, it usually decreases the genetic diversity of the cloned species, which threatens the evolution, adaptation and survival of the species when confronted with environmental change.
Cochlear implants are used to treat severe sensorineural hearing loss, but require a functioning auditory nerve. A microphone on the outside of the head detects sound which is then converted into an electrical signal which is transmitted to an electrode that is implanted along the organ of corti within the cochlea.
The electrode produces an electrical current that stimulates the nerves at the right position for that particular frequency. The signal is sent along the auditory nerve to the brain where it is perceived as sound.
Cochlear implants must be implanted in children as early as possible since most language development in the brain occurs in the first few years of life. The graph shows that when the implant is installed in children under 3 years of age only 10% of them will still be using sign language for communication after 5 years (down from 78%).
By contrast, over 50% of children will still be using sign language after 5 years if they received the implant when they were over 5 years old (a similar % to just after the implant).
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