HSC EXAM_STYLE QUESTIONS
1. Gentamicin is an antibiotic drug that is commonly used to fight various bacterial infections.
Once administered, the drug passes through the cell wall of the bacteria via protein channels
and then proceeds to irreversibly bind to parts of ribosomes that are found inside these foreign
bacterial cells.
a) Explain how gentamicin will inhibit the normal functioning of the bacterial cell
b) One such bacterium that is susceptible to gentamicin is Pseudomonas aeruginosa, a
bacterium that can be the cause of many infections such as pneumonia. Assess the
effectiveness of this antibiotic in reducing the magnitude and spread of disease.
c) One of the reasons Pseudomonas aeruginosa is a dangerous bacterium, is because it
releases exotoxin A, a protein-based toxin which results in inhibition of protein synthesis
in eukaryotic cells, including those of the human body. This toxin is considered to be part
of the ’proteome’ of the cell. In their functional states, many toxins have tertiary
structures. Describe the differences between the secondary and tertiary structure of a
protein
d)
e) Explain one mechanism of how a pathogen can adapt to facilitate its entry and
transmission between hosts
2. Scientists Alex and Will are researching the composition of DNA from a newly discovered
species of mammal. They find, through various testing, that of the nuclear genome, 27% is
composed of adenine.
a) What is the percentage (if it can be determined) of cytosine in the cell? If it cannot be
determined, explain why this is the case
b) What is the percentage (if it can be determined) of uracil in the nuclear genome? If it
cannot be determined, explain why this is the case.
3. Yellow fever is a potentially fatal, mosquito-borne, viral disease that occurs in many countries
in Africa, the Caribbean, and Central and South America. An effective and safe vaccine has
been available since 1938.
a) Once the vaccine is injected into the arm of a child, an immune response
occurs.Summarise the immune response that occurs within the child to result in
long-term protection from yellow fever.
b) For the vaccine to be effective, it is recommended that travellers to these regions have
the vaccination approximately two to four weeks before travelling. Why is this time frame
recommended?
c) If a person has not been vaccinated and is older than 14 years, it is recommended that
this person has two doses of the virus vaccine. The second dose should be given at
least four weeks after the first dose. What is the benefit of having two doses instead of
one dose? Justify your response.
d) Recent research shows that the vaccine gives lifelong immunity. Explain the process of
lifelong immunity and the requirements for this to occur.
e) Outline similarities and/or diff erences in active and passive ways of acquiring immunity
4. In a rat population, three different fur colours can be observed. The rats can have grey, black
or white fur. The production of fur colour pigment in these rats is controlled by two genes. The
two genes are not linked.
a) What conclusion can be made about the location of the two genes on the chromosomes
of these rats?
The two genes controlling the production of fur colour pigment have the following alleles.
Gene 1
G
grey pigment
Gene 2
A
pigment produced
g
black pigment
a
no pigment produced
The presence of at least one A allele allows for the production of pigment. White fur is seen in
rats without a copy of the A allele.
b) A rat has black fur. What are all the possible genotypes for this rat?
c) Two rats heterozygous with respect to Gene 1 and Gene 2 for fur colour were crossed.
What are the possible genotypes and phenotypes of the offspring? Show your working
and state the ratio for the phenotypes of the offspring
5. Two species of Cryptasterina sea stars are found in coastal Queensland. Cryptasterina
pentagona is found in warmer water further north, while Cryptasterina hystera is found further
south in cooler water.
Researchers have concluded that these two species arose from a recent common ancestor via
natural selection. They believe that, over thousands of years, the sea environment has
changed, with the boundary line between cold water and warm water moving further north. They
have found that water temperature and predation of sea star larvae by cold-water predators are
important selection pressures for these sea stars.
a) Using the information above, explain how natural selection can lead to differences in
phenotypes between these two sea star species
b) One of the phenotypic differences between these two species of sea stars is their
method of reproduction. C. pentagona reproduces sexually and its sperm and eggs are
free-floating in the ocean. C. hystera self-fertilises and its fertilised eggs are kept within
the sea star until maturity. The researchers found that one species of Cryptasterina has
a significantly higher diversity of alleles in its gene pool than the other species. Using this
information about reproduction strategies, which species of Cryptasterina would you
expect to have the highest diversity of alleles? Explain your answer.
6. Gene therapy can be used to introduce normal genes into cells to replace missing or
defective genes in order to treat or prevent disease. Scientists have taken a number of different
approaches to using gene therapy.
The following are two of these approaches:
● germline gene therapy – embryonic cells are treated to correct a missing or defective
gene
● somatic cell gene therapy – a normal gene is inserted into somatic (body) cells to correct
a missing or defective gene
a) Identify one issue that would make scientists cautious about using germline gene
therapy.
Viral vectors (adenoviruses and retroviruses) are often used in gene therapy to insert a normal
gene into target cells. Two processes that can be used are outlined below.
b) What is one advantage that ex-vivo gene therapy has over in-vivo gene therapy?
c) Explain the necessary evidence, at a cellular level, that would confirm that the processes
above were successful and compare this to the normal gene function in individuals that
naturally express this gene in their genome.
7. Consider the template strand of a hypothetical gene, shown below. The exons are in bold
type.
3′ TAC AAA CCG GCC TTT GCC AAA CCC AAC CTA AAT ATG AAA ATT 5′
Note:
1. The DNA triplet TAC indicates START and codes for the amino acid methionine that remains
in the polypeptide.
2. The DNA triplets ATC, ATT and ACT code for a STOP instruction.
a) How many amino acids would be present in the polypeptide expressed by this gene?
b) An allele for this gene codes for a polypeptide with only five amino acids. This is caused
by a mutation in one of the exons. This mutation is a result of one nucleotide change. By
referring to the original sequence above, identify the nucleotide change that must have
occurred to bring about this shorter polypeptide.
c) Hereditary retinoblastoma is a rare autosomal dominant trait. The pedigree below shows
the trait appearing in a family with no prior history of the condition before generation III.
Explain the appearance of this trait in generations III and IV
In the Australian sheep blowfly, Lucilia cuprina, eye colour can be red or white, and body bristles
(stiff hairs) can be straight or crooked. The diagram below represents a pair of homologous
autosomes from a male blowfly with red eyes and straight bristles. The gene loci for eye colour
(R) and bristle shape (B) are shown.
d) Complete the diagram below to show the genotypes of all four gametes formed in one
meiotic division in this fly.
8.
a) What is meant by recombinant deoxyribonucleic acid in the context of this article?
b) The article states that the researchers knew the structure of insulin and the amino acid
sequence before they created the recombinant human insulin in the laboratory. How
would the researchers have used this information to genetically engineer a human
insulin gene and how might this engineered insulin gene have differed from a natural
insulin gene isolated from human DNA?
c) Outline the steps that are required for the human insulin gene to be cloned and
expressed in bacteria and compare its effectiveness to another genetic technology you
have studied this year.
9. The Genomics Health Futures Mission will run a $32 million trial, starting in 2019, to screen
over 10 000 couples who are in early pregnancy or who are planning to have a baby. Using a
blood test, individuals will be screened for 500 severe or deadly recessive gene mutations.
Couples will be told they have a genetic mutation if both individuals in the couple carry the same
mutation. The trial may lead to a population-wide carrier screening program. The researchers
will evaluate cost effectiveness, psychological impact, ethics and barriers to screening. It is
anticipated that future tests will be free of charge.
a) Give an example of a disorder or disease that can be detected by genetic screening.
b) The blood sample from an individual will provide researchers with only a small amount of
DNA. Polymerase chain reaction (PCR) will be used to amplify the DNA. Describe what
happens in each of the three stages of PCR. The stages must be given in the order in
which they occur.
c) The test may fi nd that a couple who were planning to have a baby or who were already
pregnant both carry the same severe or deadly mutation. Describe one ethical and one
social issue/implication that could arise from this fi nding