Our Biology Group has been laborious at work placing collectively the options to the 2019 HSC Biology Examination. Learn the options under and see the way you went!
Part 1: A number of Alternative
| Query | Reply | Resolution |
| 1 | D | Haemophilia is genetic whereas all the opposite choices are attributable to a pathogen. |
| 2 | C | The physique produces antibodies that match the antigens current within the vaccine. |
| 3 | D | The predator acts as a variety strain, lowering the variety of darkish beetles over time. |
| 4 | D | A nucleotide consists of 1 base, one sugar and one phosphate group. |
| 5 | B | Phagocytes engulf and digest international particles. |
| 6 | C | Cochlear implants bypass the ear canal, ossicles and hair cells to electrically stimulate the auditory nerve. |
| 7 | A | Whereas antibiotic W is pretty efficient in opposition to each sorts of micro organism. |
| 8 | B | The information isn’t steady. A and D signify the variety of animals not the variety of species. |
| 9 | A | Inside fertilisation happens in an enclosed house (reproductive tract) to stop the gametes from drying out. |
| 10 | C | The variety of contaminated cattle will probably be depending on the quarantine coverage of every island. |
| 11 | B | The dominant phenotype will probably be seen in each homozygous and heterozygous people. |
| 12 | D | Sort 2 diabetics preserve blood glucose ranges above that of a non-diabetic. |
| 13 | B | Genetic drift is the change of allele frequency in a inhabitants because of random probability occasions. |
| 14 | A or B | Assuming the template strand is supplied, the complimentary mRNA strand could be GCG UAG UAC GAU so the matching anticodons could be CGC AUC AUG CUA. |
| 15 | C | A germ line mutation happens in DNA throughout meiosis within the manufacturing of a gamete. If the mutation happens in non-coding (‘junk’) DNA it’s much less prone to have any influence. |
| 16 | D | Scholar X has been uncovered to antigens from the pathogen earlier than so will expertise a secondary response. Scholar Y has not been uncovered to the antigens earlier than so will expertise a major response. Based on the graph the first response wouldn’t attain 1000 mg/L. |
| 17 | A | The inheritance sample have to be dominant as there are two affected dad and mom with an unaffected little one. It can’t be intercourse linked recessive as there may be an affected feminine with an unaffected son. |
| 18 | B | This can be a optimistic suggestions loop because the response to the stimulus leads to an additional improve to the stimulus. |
| 19 | A | Cas9 is an enzyme as it’s a reusable molecule that catalyses a response (breaking bonds between DNA bases). |
| 20 | D | gRNA has nucleotides complementary to the goal DNA in order that the Cas9 enzyme binds and cuts on the precise place required. |
Part 2: Quick response
Query 21
A rise in physique temperature is [detected by the hypothalamus in the brain]. Nerve impulses journey to blood vessels and sweat glands inflicting [vasodilation] and sweat to be produced by sweat glands. This causes extra blood move to the pores and skin and [evaporative cooling]. The result’s warmth loss from blood and a fall in physique temperature.
Query 22
| Somatic mutation | Germ-line mutation | |
| Location | Any physique cell apart from intercourse cells | Intercourse cells within the gonads solely |
| Impact on offspring | None – mutation isn’t handed on to offspring | The mutation could also be handed to offspring |
| Instance | Mutation in a pores and skin cell leading to pores and skin most cancers | Trisomy 21 – an additional copy of chromosome 21 in each cell of the offspring |
Query 23
Instructional packages are initiatives developed by the Authorities and non-government organisations with the intention to minimise the incidence of illness amongst the neighborhood. Initiatives embody consciousness ads on TV and radio, on the perimeters of buses, in faculties, medical doctors’ surgical procedures or at school packages akin to life schooling. These initiatives affect way of life modifications that can scale back the incidence of non-infectious illness. For instance, epidemiological research have recognized a relationship between U.V. publicity and pores and skin most cancers, in addition to cigarette smoking and lung most cancers. In response, the Australian Authorities has developed campaigns to extend consciousness and affect way of life modifications to stop the incidence of lung most cancers. After the introduction of the ‘give up now’ marketing campaign in 1997-98 it was discovered that there was a 1.8-3.1% discount within the prevalence of smoking inside 18 months of the beginning of the marketing campaign.
Query 24
Synthetic insemination is the gathering and handbook placement of sperm into the feminine reproductive tract. That is typically used to selectively breed two organisms of the identical species with beneficial traits. For instance, impregnating a mare with out requiring the stallion to be in the identical location. Synthetic insemination can improve biodiversity on the genetic stage because it permits crosses that will not usually happen because of distance or bodily variations. Nevertheless, sperm from the identical male can be utilized many instances and this could result in elevated ranges of those genes throughout the inhabitants i.e. decreased genetic variety.
Transgenic species in agriculture initially improve genetic variety by introducing genes from one species to a different e.g. Bt cotton that has a gene from a bacterium. A drawback is that transgenic organisms are often cloned which reduces biodiversity because it means massive areas of crop are genetically similar. Bt cotton has a bonus and should outcompete native species, lowering ecosystem biodiversity.
Query 25
(a) People often have two intercourse chromosomes, XX in females and XY in males. This karyotype has just one intercourse chromosome (X).
(b) The karyotype above is an instance of aneuploidy on account of non-disjunction throughout meiosis. Every daughter cell produced throughout meiosis ought to have N chromosomes, however in some instances non-disjunction happens the place chromosomes don’t separate correctly throughout Anaphase I or Anaphase II producing some daughter cells with N+1 and a few cells with N-1. On this case, throughout fertilisation a N-1 gamete has mixed with a standard N gamete to provide a 2N-1 karyotype within the zygote. This particular karyotype would end in Turner syndrome.
Query 26
Within the areas with a excessive share of the inhabitants capable of digest lactose (e.g. Northern Europe, Western Africa) it’s probably that previously cow’s milk was used as an vital meals supply. There would have been durations the place different sources of meals failed and people that might not digest lactose perished and didn’t go their genes to the following technology. By way of this technique of pure choice, these with a mutation that allowed them to provide the lactase enzyme for longer would have survived and handed on their genes. In areas the place milk is much less out there, the mutation isn’t prone to be handed on and develop into frequent within the inhabitants.
Whereas there’s a protein coding gene answerable for the manufacturing of the lactase enzyme, it isn’t on this gene the place the mutation has occurred. What has modified is when the gene is switched on and off, which is managed by different DNA areas (e.g. promotors, inhibitors, silencers).
Query 27
(a) Budding is a type of asexual copy.
(b) As yeast reproduces and its biomass will increase, the yeast converts glucose into carbon dioxide and ethanol in a fermentation response. Due to this fact, carbon dioxide fuel can be utilized as an indicator of copy fee.
1. Develop a tradition of yeast by including 500ml of development media (containing 20g of sucrose) and 20g of yeast to a 1L flask. Incubate at room temperature for twenty-four hours.
2. Pour 100ml of development media into 4 500ml flasks. Label the flasks 4oC, room temperature (~24 oC), 30 oC and 40 oC.
3. Combine the tradition produced in step 1, take 4 1ml samples and add them to every of the flasks.
4. Place the 4 oC flask into the fridge, the 30 oC flask into an incubator set at 30 oC and the 40 oC flask into an incubator set to 40 oC. Depart the room temperature flask on the bench. Incubate the flasks for six hours on the assigned temperatures.
5. For every flask, combine and take three 1mL samples. Swirl every pattern evenly over a separate agar plate.
6. Incubate plates for two days at room temperature and use a microscope and mm grid to rely the variety of colonies fashioned on every plate. Document outcomes.
7. Steps 1-6 must be repeated 3 instances.
Query 28
(a) The affected person inherited H and r alleles from the daddy, h and R from the mom.
(b)
| Chromosome I | Chromosome II | |||
| Earlier than crossing over | r r
H H |
R R
h h |
||
| After crossing over | r r
— H h |
R R
— H h |
||
| Gametes | r
H |
r
H |
R
H |
R
h |
Key: r = Stargardt illness, R = regular retina, H = Huntington’s illness, h = regular nerve cells
Query 29
Water loss have to be managed in vegetation or the plant won’t be able to carry out photosynthesis and it’ll lose turgor strain and wilt. When there may be adequate water out there, the guard cells of the stomata swell up (develop into turgid), this bends them and opens up the pore for fuel trade. When water ranges drop the guard cell shrinks, closing off the pore. Closing is triggered by the stress hormone abscisic acid and prevents evaporation of water (but additionally prevents fuel trade for photosynthesis).
Query 30
If the unique dad and mom had been pure breeding (homozygous) the F1 technology will all be heterozygous. For seed form, the F2 technology reveals the standard 3:1 ‘Mendelian’ ratio of phenotypes of offspring seen when crossing two heterozygous dad and mom with alleles which have a easy dominant/recessive relationship. For instance if R = spherical seeds and r = wrinkled seeds
| R | r | |
| R | RR | Rr |
| r | Rr | rr |
When the F1 technology is bred collectively 3 genotypes are produced: RR (25%), Rr (50%) and rr (25%). Nevertheless because of the presence of the dominant allele solely two phenotypes are produced: Spherical (75%) and wrinkled (35%).
Against this crossing two heterozygous dad and mom from the F1 technology has produced three completely different phenotypes for feather color. This means a case of incomplete dominance or co-dominance (as proven within the punnet sq. under). If FB = black feathers and FW = white feathers
| FB | FW | |
| FB | FBFB | FBFW |
| FW | FBFW | FWFW |
In a case of co-dominance the F2 technology can have 25% birds with black feathers, 25% with solely white feathers and 50% of birds can have speckled (black and white) feathers. Within the case of incomplete dominance 50% of birds would have gray feathers somewhat than speckled..
Query 31
(a) The bacterium that causes the plague (Yersinia pestis) makes use of fleas as a vector with the intention to bypass the primary line of defence (pores and skin). When an individual is bitten the bacterium leaves the flea and enters the blood stream of the human host.
(b) Infectious ailments can unfold by direct or oblique transmission. In direct contact transmission there may be some bodily contact between an contaminated particular person and a prone particular person e.g. mucus droplets unfold the frequent flu virus. This causes ailments to unfold rapidly in densely populated areas. In oblique contact transmission there isn’t any direct human-to human contact e.g. chew from insect vector causes Malaria. The unfold of the illness could also be simpler to manage.
Query 32
(a) Between 1900 to 2010 there was a rise within the human inhabitants from 1.2 to six.8 billion and a rise within the precise variety of folks susceptible to Malaria from 0.9 billion to three.4 billion. Regardless of this, the share of the inhabitants susceptible to Malaria has truly decreased from 75% to 50% and the variety of nations that have instances of Malaria has declined from 140 to 88. Against this, reported instances of dengue fever has elevated from 1950 to 2010 and the illness has unfold to many extra nations and continents in that point (e.g. South America, Africa, Australia).
(b) For the reason that world inhabitants has elevated, with many individuals dwelling in excessive density areas, this gives a possibility for ailments akin to Dengue fever and Malaria to unfold. Nevertheless, Malaria is a illness that has occurred within the human inhabitants for hundreds of years and in contrast dengue is a comparatively new illness occurring between 100-800 years in the past and has been restricted geographically till the Fifties, this makes a lot of the human inhabitants prone hosts that would not have immunity to the illness. Whereas Malaria is attributable to the plasmodium parasite, Dengue fever is a virus that has quite a lot of strains and may mutate simply, additional stopping populations from growing immunity. This will assist clarify distribution of Malaria has diminished (from 140 nations reporting right down to 88), whereas between 1950 and 2010 the variety of nations reporting dengue fever has elevated.
Traditionally there was extra consciousness of Malaria and the mosquito vector that spreads it. There was a World Malaria Eradication program began in 1955 which used methods akin to DDT pesticide spraying, draining of swamps and distribution of mattress nets. There was a 14% lower within the inhabitants in danger between 1946 and 1975 indicating that the packages succeeded in eradicating the illness in sure areas. Dengue fever has not attracted the identical consideration and coordinated international elimination packages. In truth it’s known as a ‘uncared for tropical illness’.
Worldwide commerce and journey growth (e.g. frequency of worldwide flights) has elevated quickly because the Fifties which might transport contaminated folks and the mosquito vectors that unfold these ailments. Nevertheless, one other distinction between Malaria and Dengue is that there isn’t any efficient antiviral therapy for Dengue. This implies extra contaminated people which might be sick for longer and may unfold the illness to others. Against this, Malaria may be handled successfully with medicines akin to Coartem or chloroquine which prevents the illness from spreading additional (for each Dengue and Malaria, vaccinations have had minimal effectiveness so far).
Query 33
(a) Within the nucleus the gene/s for amyloid beta are copied onto an mRNA strand by RNA polymerase within the nucleus (Transcription). Within the cytoplasm a Ribosome will endure Translation of the mRNA strand right into a string of amino acids. The tRNA molecules with anticodons that match the codons on the mRNA ship amino acids to the ribosome that joins them along with peptide bonds. This creates a polypeptide chain or a number of chains which will probably be folded and modified to develop into amyloid beta protein.
(b)(i) Alleles are different types of a gene. Whereas a person can solely carry 2 alleles for a gene, for a lot of genes there are greater than two completely different alleles for a gene within the inhabitants. For instance clover has 7 completely different alleles for leaf sample leading to 22 completely different doable genotypes for leaf sample.
(ii) The e2, e3 and e4 alleles are every related to a threat stage for Alzheimer’s, and the completely different alleles work together with one another to provide completely different threat ranges. Allele e3 produces a mean threat, whereas e2 appears to be a protecting issue for this illness, lowering the chance of growing Alzheimer’s by 40% (e2 is dominant over e3). Inheriting a duplicate of e4 will increase the danger of growing Alzheimer’s, even together with e2. Inheriting two copies of the e4 allele makes growing Alzheimer’s 14.9 instances extra probably. Due to this fact, inheriting a number of e2 alleles reduces threat of Alzheimer’s whereas a number of e4 alleles will increase the danger of Alzheimer’s growing.
(c) Of the three teams, people with untreated Herpes Simplex Virus have the next threat of dementia and this threat will increase with the variety of years that go. After 11 years of comply with up the cumulative threat of dementia for this group greater than twice that of the group that was handled with antivirals. For these with HSV an infection that was handled with antivirals the danger will increase far more slowly and after 11 years the cumulative threat is 1. The danger of dementia nonetheless will increase over time for these with none HSV an infection however solely very barely (lower than 0.5 after 11 years).
(d) Infectious ailments are attributable to a pathogen and may be handed from individual to individual whereas non-infectious ailments can’t be handed on to a different particular person besides by way of inheritance. Not one of the data supplied in Q33 means that an individual with Alzheimer’s illness signs can go this illness on to a different particular person by way of direct or oblique contact. Nevertheless, the desk in 33 (b) reveals that the genotype of a person has a really sturdy affect over whether or not a person develops Alzheimer’s. A person with two dangerous e4 alleles has 14.9 instances greater threat of Alzheimer’s and with two e2 alleles the illness is 40% much less probably. This means it must be classed as a non-infectious illness.
The graph in 33(C) reveals there may be an elevated threat of dementia after Herpes Simplex Virus an infection, however Alzheimer’s isn’t the one explanation for dementia, so it’s unclear precisely how the graph pertains to the danger of Alzheimer’s illness. The graph additionally reveals that even those who haven’t skilled HSV an infection present a gradual improve in threat of dementia over time which signifies that HSV isn’t the one explanation for the illness.
A approach to set up whether or not Alzheimer’s is attributable to a pathogen could be to make use of Koch’s postulates which had been developed with the intention to establish which microbes are related to a particular illness. If the postulates had been to be adopted:
- All people with Alzheimer’s illness could be discovered to have the identical pathogen inside their system.
- The pathogen could be remoted, recognized and cultured.-When a wholesome particular person was contaminated with the aesthetic pathogen they’d develop signs of Alzheimer’s illness.
- The pathogen could be identifiable within the newly contaminated host.
- Whereas such a experiment wouldn’t be moral to carry out in people it may very well be tried in mice.
Along with genetic elements and HSV an infection, Alzheimer’s illness has additionally been related to bacterial an infection, gender, head harm and levels of cholesterol. Due to this fact, there appear to be a number of elements that have an effect on the danger of Alzheimer’s and a single pathogen alone isn’t accountable. At this level Alzheimer’s illness must be labeled as a non-infectious illness. Additional research are wanted to disclose the particular function of pathogens in growth of the illness.
