Biology

Agrobacterium tumefaciens is a rod-shaped bacterium found in soil. Its flagella allow it to move through the soil in response to chemicals released by wounded plant cells. Once it enters its plant host, it injects a section of its DNA called the T-DNA which is derived from its Ti (tumour inducing) plasmid into its host causing the host to form undifferentiated (tumour) tissue termed a crown gall. Figure 1: Crown gall The interaction between a plant and Agrobacterium is detailed below: (A) Agrobacteria cells produce the hormones cytokinin and auxin, which increase host susceptibility and inhibit H2O2 production and hypersensitive response (HR) upon infection. (B) After integration of the bacterial T-DNA into the plant genome, cytokinin and auxin are synthesized by T-DNA encoded enzymes and accumulate inside the tumour. (C) This causes massive changes in the gene expression pattern resulting in metabolomic and morphological adaptations that are necessary for tumour growth and differentiation. (D) Loss of water is minimized by an increase in the levels of the stress hormone ABA. Evaporation of water from the disrupted crown gall surface drives the flow of water and minerals into crown galls. (E) Because photosynthesis is downregulated, the O2 levels are low, the tumour produces C and N compounds heterotrophically and gains energy mainly anaerobically by alcoholic fermentation. (F) The developing tumour becomes a metabolic sink for the host plant, which accumulates metabolites produced by source leaves and minerals taken up by the roots. (G) Auxin and cytokinin also cause an increase in ethylene (ET) which together with salicylic acid (SA) inhibits agrobacterial virulence. (H) ABA induces DNA methylation of the plant genome, regulating gene expression of drought- stress responsive genes. The oncogenes of the T-DNA remain unaffected by methylation of the plant genome.

Describe ONE adaptation that makes agrobacterium a successful pathogen of plants.

Rubella is an infectious disease caused by Rubivirus rubella. The disease is frequently mild, with a characteristic rash often appearing two weeks after exposure and lasting for three days. Other symptoms include fever, sore throat and fatigue, with joint pain common in adults. Up to half of infected cases are asymptomatic. Rubella is usually spread from one person to the next through the air via coughs of people who are infected. People are infectious during the week before and after the appearance of the rash. Only humans are infected. Once recovered, people are immune to future infections. In the early 1940s, Australian ophthalmologist Norman Gregg noticed a high incidence of congenital cataracts in babies whose mothers had suffered from rubella during pregnancy. It was then statistically shown that infection during early pregnancy may result in a miscarriage or a child born with congenital rubella syndrome (CRS). The main defects result almost exclusively from rubella infection occurring in the first 16 weeks of gestation and include deafness due to cochlea malformation, eye and cardiovascular defects and central nervous system damage leading to mental retardation. Rubella is preventable with a single dose of the rubella vaccine being more than 95% effective. When rubella vaccination became feasible around 1971, both the United States and the United Kingdom embarked on vaccination programs. In the United States, the strategy was to vaccinate infants, so that eventually the reservoir in childhood would be abolished. In contrast, the United Kingdom decided on a program of vaccinating adolescent girls. Both strategies were partial successes, in that CRS incidence began to decrease.

Evaluate the importance of validity in biological research. In your response, refer to:
• the study that you have described in part (f),
• ONE other named epidemiological study that you have investigated as part of your course
• ONE first-hand investigation that you have carried out as part of your course
• ONE second-hand investigation that you have carried out as part of your course

Rubella is an infectious disease caused by Rubivirus rubella. The disease is frequently mild, with a characteristic rash often appearing two weeks after exposure and lasting for three days. Other symptoms include fever, sore throat and fatigue, with joint pain common in adults. Up to half of infected cases are asymptomatic. Rubella is usually spread from one person to the next through the air via coughs of people who are infected. People are infectious during the week before and after the appearance of the rash. Only humans are infected. Once recovered, people are immune to future infections. In the early 1940s, Australian ophthalmologist Norman Gregg noticed a high incidence of congenital cataracts in babies whose mothers had suffered from rubella during pregnancy. It was then statistically shown that infection during early pregnancy may result in a miscarriage or a child born with congenital rubella syndrome (CRS). The main defects result almost exclusively from rubella infection occurring in the first 16 weeks of gestation and include deafness due to cochlea malformation, eye and cardiovascular defects and central nervous system damage leading to mental retardation. Rubella is preventable with a single dose of the rubella vaccine being more than 95% effective. When rubella vaccination became feasible around 1971, both the United States and the United Kingdom embarked on vaccination programs. In the United States, the strategy was to vaccinate infants, so that eventually the reservoir in childhood would be abolished. In contrast, the United Kingdom decided on a program of vaccinating adolescent girls. Both strategies were partial successes, in that CRS incidence began to decrease. Figure 1: Number of Rubella and Congenital Rubella Syndrome Cases in the United States 1966-2011
Justify a hypothesis as to why the UK program was only a partial success in reducing the rate of CRS.
Hypothesis:………………………………………………………………………………………
Justification:………………………………………………………………………………………

Rubella is an infectious disease caused by Rubivirus rubella. The disease is frequently mild, with a characteristic rash often appearing two weeks after exposure and lasting for three days. Other symptoms include fever, sore throat and fatigue, with joint pain common in adults. Up to half of infected cases are asymptomatic. Rubella is usually spread from one person to the next through the air via coughs of people who are infected. People are infectious during the week before and after the appearance of the rash. Only humans are infected. Once recovered, people are immune to future infections. In the early 1940s, Australian ophthalmologist Norman Gregg noticed a high incidence of congenital cataracts in babies whose mothers had suffered from rubella during pregnancy. It was then statistically shown that infection during early pregnancy may result in a miscarriage or a child born with congenital rubella syndrome (CRS). The main defects result almost exclusively from rubella infection occurring in the first 16 weeks of gestation and include deafness due to cochlea malformation, eye and cardiovascular defects and central nervous system damage leading to mental retardation. Rubella is preventable with a single dose of the rubella vaccine being more than 95% effective. When rubella vaccination became feasible around 1971, both the United States and the United Kingdom embarked on vaccination programs. In the United States, the strategy was to vaccinate infants, so that eventually the reservoir in childhood would be abolished. In contrast, the United Kingdom decided on a program of vaccinating adolescent girls. Both strategies were partial successes, in that CRS incidence began to decrease.

Describe the trends in the incidence of infectious rubella cases.

Rubella is an infectious disease caused by Rubivirus rubella. The disease is frequently mild, with a characteristic rash often appearing two weeks after exposure and lasting for three days. Other symptoms include fever, sore throat and fatigue, with joint pain common in adults. Up to half of infected cases are asymptomatic. Rubella is usually spread from one person to the next through the air via coughs of people who are infected. People are infectious during the week before and after the appearance of the rash. Only humans are infected. Once recovered, people are immune to future infections. In the early 1940s, Australian ophthalmologist Norman Gregg noticed a high incidence of congenital cataracts in babies whose mothers had suffered from rubella during pregnancy. It was then statistically shown that infection during early pregnancy may result in a miscarriage or a child born with congenital rubella syndrome (CRS). The main defects result almost exclusively from rubella infection occurring in the first 16 weeks of gestation and include deafness due to cochlea malformation, eye and cardiovascular defects and central nervous system damage leading to mental retardation. Rubella is preventable with a single dose of the rubella vaccine being more than 95% effective. When rubella vaccination became feasible around 1971, both the United States and the United Kingdom embarked on vaccination programs. In the United States, the strategy was to vaccinate infants, so that eventually the reservoir in childhood would be abolished. In contrast, the United Kingdom decided on a program of vaccinating adolescent girls. Both strategies were partial successes, in that CRS incidence began to decrease. Figure 1: Number of Rubella and Congenital Rubella Syndrome Cases in the United States 1966-2011

Use the evidence in the graph to justify the statement that the US program was only a partial success in reducing the rate of CRS.

Rubella is an infectious disease caused by Rubivirus rubella. The disease is frequently mild, with a characteristic rash often appearing two weeks after exposure and lasting for three days. Other symptoms include fever, sore throat and fatigue, with joint pain common in adults. Up to half of infected cases are asymptomatic. Rubella is usually spread from one person to the next through the air via coughs of people who are infected. People are infectious during the week before and after the appearance of the rash. Only humans are infected. Once recovered, people are immune to future infections. In the early 1940s, Australian ophthalmologist Norman Gregg noticed a high incidence of congenital cataracts in babies whose mothers had suffered from rubella during pregnancy. It was then statistically shown that infection during early pregnancy may result in a miscarriage or a child born with congenital rubella syndrome (CRS). The main defects result almost exclusively from rubella infection occurring in the first 16 weeks of gestation and include deafness due to cochlea malformation, eye and cardiovascular defects and central nervous system damage leading to mental retardation. Rubella is preventable with a single dose of the rubella vaccine being more than 95% effective. When rubella vaccination became feasible around 1971, both the United States and the United Kingdom embarked on vaccination programs. In the United States, the strategy was to vaccinate infants, so that eventually the reservoir in childhood would be abolished. In contrast, the United Kingdom decided on a program of vaccinating adolescent girls. Both strategies were partial successes, in that CRS incidence began to decrease. Figure 1: Number of Rubella and Congenital Rubella Syndrome Cases in the United States 1966-2011

Today, most developed countries have a comprehensive immunization program and rubella has been eliminated in many areas of the world. However, in a number of developing countries rubella infections are common and significant number of babies are born with CRS.
Explain how a named medical technology could be used to treat a symptom of CRS and propose a reason why this is not routinely done.

Rubella is an infectious disease caused by Rubivirus rubella. The disease is frequently mild, with a characteristic rash often appearing two weeks after exposure and lasting for three days. Other symptoms include fever, sore throat and fatigue, with joint pain common in adults. Up to half of infected cases are asymptomatic. Rubella is usually spread from one person to the next through the air via coughs of people who are infected. People are infectious during the week before and after the appearance of the rash. Only humans are infected. Once recovered, people are immune to future infections. In the early 1940s, Australian ophthalmologist Norman Gregg noticed a high incidence of congenital cataracts in babies whose mothers had suffered from rubella during pregnancy. It was then statistically shown that infection during early pregnancy may result in a miscarriage or a child born with congenital rubella syndrome (CRS). The main defects result almost exclusively from rubella infection occurring in the first 16 weeks of gestation and include deafness due to cochlea malformation, eye and cardiovascular defects and central nervous system damage leading to mental retardation. Rubella is preventable with a single dose of the rubella vaccine being more than 95% effective. When rubella vaccination became feasible around 1971, both the United States and the United Kingdom embarked on vaccination programs. In the United States, the strategy was to vaccinate infants, so that eventually the reservoir in childhood would be abolished. In contrast, the United Kingdom decided on a program of vaccinating adolescent girls. Both strategies were partial successes, in that CRS incidence began to decrease.

The mechanism for how CRS occurs is not clear, although it is known that the pathogen crosses the placenta and infects the embryo. It appears that the rate of mitosis in some embryonic tissues is decreased. Explain how a reduced rate of mitosis could cause ONE identified symptom of CRS

Rubella is an infectious disease caused by Rubivirus rubella. The disease is frequently mild, with a characteristic rash often appearing two weeks after exposure and lasting for three days. Other symptoms include fever, sore throat and fatigue, with joint pain common in adults. Up to half of infected cases are asymptomatic. Rubella is usually spread from one person to the next through the air via coughs of people who are infected. People are infectious during the week before and after the appearance of the rash. Only humans are infected. Once recovered, people are immune to future infections. In the early 1940s, Australian ophthalmologist Norman Gregg noticed a high incidence of congenital cataracts in babies whose mothers had suffered from rubella during pregnancy. It was then statistically shown that infection during early pregnancy may result in a miscarriage or a child born with congenital rubella syndrome (CRS). The main defects result almost exclusively from rubella infection occurring in the first 16 weeks of gestation and include deafness due to cochlea malformation, eye and cardiovascular defects and central nervous system damage leading to mental retardation. Rubella is preventable with a single dose of the rubella vaccine being more than 95% effective. When rubella vaccination became feasible around 1971, both the United States and the United Kingdom embarked on vaccination programs. In the United States, the strategy was to vaccinate infants, so that eventually the reservoir in childhood would be abolished. In contrast, the United Kingdom decided on a program of vaccinating adolescent girls. Both strategies were partial successes, in that CRS incidence began to decrease.

An alternative hypothesis for the mechanism is that some of the symptoms of CRS are due to maternal infection causing malfunction of the mother’s liver resulting in excessively high (toxic) levels of Vitamin A in the blood of both the mother and the developing embryo. Vitamin A is stored in the liver and is also found in the diet in cheese, dairy, liver and meat.
A group of unvaccinated pregnant women in a developing region has just been exposed to rubella virus.
Outline an epidemiological study that could be carried out ethically to test the Vitamin A hypothesis outlined above.

In maintaining homeostasis, which of the following is a behavioural adaptation?
A. Sweating to cool down
B. Curling up in a ball to keep warm
C. Speeding up or slowing down cell metabolism
D. Skin going red as more blood flows to surface

Sexual reproduction in plants involves
A. pollination caused by dispersal of seeds.
B. cloning as it creates copies of the parent plant.
C. mitosis leading to the formation of pollen grains.
D. fertilisation as a result of fusion of male and female gametes.

The following four events occur during reproduction in a placental mammal. 1. Fertilisation 2. Implantation 3. Ovulation 4. Placental formation In which order do these events occur?
A. 2, 1, 3, 4
B. 2, 4, 1, 3
C. 3, 1, 2, 4
D. 3, 2, 4, 1

Malaria is a disease in humans caused by a single-celled Plasmodium species. It is transmitted by female mosquitoes. Which of the following is true for malaria?
A. Both Plasmodium and the mosquito are vectors
B. Both Plasmodium and the mosquito are pathogens
C. The mosquito is the vector and Plasmodium is the pathogen
D. The mosquito is the pathogen and Plasmodium is the vector

Which row of the table best describes DNA in both prokaryotic and eukaryotic cells? Prokaryotic Eukaryotic

Citrus canker is a bacterial disease that originates in south-east Asia and affects citrus fruit. What would be the most effective way to prevent the disease from spreading into or across Australia?
A. Monitor citrus trees and fruit continuously.
B. Certify orchards before fruit is transported.
C. Keep citrus trees and fruit entering Australia in quarantine stations until the incubation period has passed.
D. Inspect citrus trees and fruit entering Australia in quarantine stations before transportation across Australia.

Students designed and conducted an investigation to test for the presence of microbes in THREE different food samples. They inoculated agar plates with the samples and placed them in an incubator set to 25°C.
Which row of the table represents a valid design for the investigation?

Quarantine is ineffective as a measure to control non-infectious diseases because they
A. cannot develop in isolation.
B. depend on long-term exposure to a pathogen.
C. may be inherited and affect the organism all their life.
D. may only be treated by genetic engineering altering cells.

A public education campaign was developed with the aim of lowering the incidence of skin cancer in the population. The campaign was adopted Australia wide and is illustrated in the poster. Protect yourself in five ways from skin cancer SLIP SLOP SLAP SEEK SLIDE Which is the best method to measure the effectiveness of the campaign?

A farmer intends to artificially inseminate cows with semen from a bull which has been chosen based on characteristics of colour and muscle mass. The farmer does not know that the bull is heterozygous for a rare recessive allele not previously present in the farmer’s cow population. The introduction of this recessive allele to the population of cows is an example of
A. gene flow.
B. genetic drift.
C. natural selection.
D. selective breeding.

The diagram shows a model of the human eye. I II Which of the following correctly identifies a labelled part and its function?

What is the purpose of cloning in agriculture?
A. Increasing the frequency of recessive traits
B. Preserving favourable traits in the offspring
C. Preserving genetic variability in a population
D. Increasing combinations of alleles in a population

A normal allele results in liver cells with sufficient cholesterol receptors. A different allele results in liver cells without cholesterol receptors. Individuals who are heterozygous have liver cells with insufficient cholesterol receptors. What type of inheritance is the most likely explanation for this?
A. Sex-linked
B. Autosomal dominant
C. Autosomal recessive
D. Incomplete dominance

Four antiviral drugs have been tested in a culture of human cells for their effectiveness in inhibiting infection from a new virus. The toxicity of the antivirals to human cells was also tested.
The ability of the drugs to inhibit viral entry to the cells (% inhibition) and the proportion of the cells killed by the drugs (% toxicity) were recorded at different doses of each drug and shown in the graphs.
From the results shown, which antiviral drug is the safest and most effective at a dose of 1 µ mol L–1?

Analysis of DNA shows that adenine and guanine always make up 50% of the total amount of nitrogenous bases in DNA. Which structural feature of DNA does this provide evidence for?
A. DNA is helical in structure.
B. DNA is always a double-stranded molecule.
C. DNA always has adenine paired with guanine.
D. DNA is made up of equal amounts of nitrogenous bases.