gcseprep.com … · Web viewThe graph shows the levels of NAD dehydrogenase in different tissues...
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Topic 7 – Modern Genetics Q1. In July 2014, scientists announced that 'Tpl2-KO' knockout mice were resistant to inflammation of the spinal cord. Describe what is meant by 'Tpl2-KO' knockout mice. (2) .............................................................................. ............................................................... .............................................................................. ............................................................... .............................................................................. ............................................................... .............................................................................. ............................................................... .............................................................................. ............................................................... Q2. In July 2014, scientists announced that 'Tpl2-KO' knockout mice were resistant to inflammation of the spinal cord. A different knockout mouse strain, called P50, has also been developed. Premature ageing can be caused by overactive NAD dehydrogenase. This enzyme is found in mitochondria. This enzyme can cause a build-up of superoxides that damage the mitochondria. The graph shows the levels of NAD dehydrogenase in different tissues of P50 mice and in wild type (WT) mice. Significance levels for p are also shown. ∗∗∗ -p < 0.001; ∗∗ -p < 0.01
Transcript of gcseprep.com … · Web viewThe graph shows the levels of NAD dehydrogenase in different tissues...
Topic 7 – Modern Genetics
Q1.
In July 2014, scientists announced that 'Tpl2-KO' knockout mice were resistant to inflammation of the spinal cord.
Describe what is meant by 'Tpl2-KO' knockout mice.
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Q2.
In July 2014, scientists announced that 'Tpl2-KO' knockout mice were resistant to inflammation of the spinal cord.
A different knockout mouse strain, called P50, has also been developed.
Premature ageing can be caused by overactive NAD dehydrogenase. This enzyme is found in mitochondria.
This enzyme can cause a build-up of superoxides that damage the mitochondria.
The graph shows the levels of NAD dehydrogenase in different tissues of P50 mice and in wild type (WT) mice. Significance levels for p are also shown.
∗∗∗ -p < 0.001; ∗∗ -p < 0.01
Use the information in the graph to predict the probability of damage occurring to the mitochondria in the organs shown.
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Q3.
Monoclonal antibodies can be made against a wide range of different antigens. They are used in research and medicine.
Monoclonal antibodies are made by fusing an antibody-producing cell with a myeloma cell.
The diagram shows some of the steps involved in making monoclonal antibodies against human cancer
cell antigens.
The antibodies made by this method are called 'mouse anti-human antibodies'. These antibodies are made by a mouse but are specific to human antigens.
Mouse anti-human antibodies are humanised using recombinant DNA methods.
The diagram shows a mouse anti-human antibody and a humanised antibody.
(i) Explain the advantages of using humanised antibodies in the treatment of cancer.
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* (ii) Explain why mouse anti-human antibodies need to be humanised in order to treat cancer.
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(Total for question = 9 marks)
Q4.
Tapirs are nocturnal mammals that are found in South America.
In 2013, the Journal of Mammalogy published an article describing the discovery of a new species of tapir, Tapirus kabomani.
Scientists already knew about the animal but thought that it was the same species as Tapirus terrestris.
(a) Give one reason why scientists thought that Tapirus kabomani was the same species as Tapirus terrestris.
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(b) These two species of tapir can be distinguished using gene sequencing.
Describe how sufficient amounts of DNA could be obtained in preparation for gene sequencing.(4)
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(c) Explain how distinguishing Tapirus kabomani as a separate species could affect the index of diversity of the area.
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(Total for question = 7 marks)
Q5.
Plasmids with genes for resistance to antibiotics are widely used in gene technology. These plasmids are used to create recombinant bacteria.
Explain how culturing could be used to obtain recombinant bacteria.
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(Total for question = 5 marks)
Q6.
Chester Zoo has 12 000 animals from 400 different species.
Chester Zoo aims "to be a major force in conserving biodiversity worldwide".
Chester Zoo supports an in-situ rhinoceros conservation and monitoring project in Chyulu Hills National Park in Kenya.
It is difficult to find and count the black rhinoceros because they roam freely across a large area.
However, the DNA of a black rhinoceros can be obtained from its dung (faeces).
(i) Devise a method by which black rhinoceros dung could be used to estimate the number of black rhinoceros living in Chyulu Hills National Park.
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(ii) DNA from dung indicated that 14 black rhinoceros were present in the park.
Explain why 14 black rhinoceros could be an underestimate of the population.(2)
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Q7.
Mouse embryonic fibroblasts can be converted into F-class ('fuzzy') pluripotent cells.
Scientists have shown that DNA demethylation may be involved in this conversion.
Explain how demethylation of DNA might cause this conversion.
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Q8.
Monoclonal antibodies can be made against a wide range of different antigens. They are used in research and medicine.
Monoclonal antibodies are made by fusing an antibody-producing cell with a myeloma cell.
The diagram shows some of the steps involved in making monoclonal antibodies against human cancer cell antigens.
Epigenetic modification is involved in the formation of the antibody-producing cells.
Describe epigenetic modification.
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(Total for question = 3 marks)
Q9.
A sea urchin is an invertebrate animal that lives on the seabed.
The photograph shows a sea urchin.
Sea urchin embryos are often used to study embryonic development. In the early stages of embryonic development, a sea urchin embryo is similar to a mammalian embryo.
Explain why the use of sea urchin embryos was approved by an ethics committee.
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Q10.
Retinitis pigmentosa is a genetic eye disease that affects rod cells. The disease results in night blindness and sight defects.
Induced pluripotent stem cells (iPS cells) are being used by scientists studying this disease.
(a) Which of the following is correct for a pluripotent cell?
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(b) Describe how iPS cells can be produced.
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(c) Describe how iPS cells could be used to cure retinitis pigmentosa.
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(Total for question = 6 marks)
Q11.
A sea urchin is an invertebrate animal that lives on the seabed.
The photograph shows a sea urchin.
Sea urchin embryos are often used to study embryonic development. In the early stages of embryonic development, a sea urchin embryo is similar to a mammalian embryo.
A scientist carefully removed one of the 128 cells from the hollow structure and injected fluorescent dye into its cytoplasm
She replaced this cell in a new position on the opposite side of the hollow structure.
The embryo then developed normally. The repositioned cell formed healthy tissue, appropriate to its new position.
The tissue formed by an embryonic cell is called the 'fate' of the cell.
(i) Explain how the scientist could identify the fate of the repositioned cell.
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(ii) The scientist found that repositioning this cell changed its fate.
Explain the scientist's finding.(4)
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Q12.
A molecule of tRNA is made from a precursor molecule that is modified. Modification includes splicing, trimming and attachment of new nucleotides.
The diagram shows a precursor molecule for a tRNA specific for the amino acid proline, and a tRNA molecule specific for the amino acid proline. Some of the bases are shown in each diagram.
Describe how this precursor molecule is modified to produce a tRNA molecule specific for the amino acid proline.
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(Total for question = 3 marks)
Q13.
Soya beans are an important crop for the production of food and oil.
A study of the nutritional content of soya beans from non-transgenic soya bean plants and from transgenic soya beans plants was carried out in two regions of Brazil.
The regions were Ponta Grossa and Londrina.
Tables 1 and 2 show the results of this study.
Table 1
Table 2
* (i) Analyse the data to assess the nutritional content of soya beans from transgenic and from non-transgenic soya bean plants grown in these two regions.
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(ii) The soil in Londrina is more fertile than the soil in Ponta Grossa. Londrina has higher temperatures and rainfall during the growing season.
Explain the differences in the nutritional content of soya beans grown in these two regions.(5)
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(iii) Explain why this study also analysed the types of fatty acid found in soya beans from transgenic plants and from non-transgenic plants.
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(Total for question = 13 marks)
Q14.
In July 2014, scientists announced that 'Tpl2-KO' knockout mice were resistant to inflammation of the spinal cord.
Genetic modification of mammals can be carried out using microinjection of recombinant DNA. Microinjection of DNA has a low success rate.
The photograph shows this technique being carried out using a micropipette.
In an investigation, 275 eggs were microinjected with DNA. Eight of these resulted in the birth of a live mammal, one of which was transgenic.
(i) Calculate the percentage success rate for producing transgenic offspring.
Give your answer to two significant figures.
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Answer ........................................................... %
(ii) The success rate of DNA microinjection is lower in plants.
Plant cells have a cell wall and an internal turgor pressure. The micropipette used for DNA microinjection can cause a drastic loss of pressure and the plant cell dies.
An alternative technique is to place protoplasts into polyethylene glycol (PEG) containing the DNA. A protoplast is a plant cell with its cell wall removed.
PEG stimulates endocytosis.
This alternative technique had a success rate of up to 20% for producing genetically modified plants.
Analyse this information to explain why this alternative technique has increased the success rate of genetic modification.
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Q15.
'DELLA' proteins normally prevent transcription factors from binding to important growth-stimulating genes in the cells of plant stems.
The diagram below shows part of the biochemical pathway leading to the synthesis of an active plant growth substance called gibberellin (GA1). GA1 reduces the effect of 'DELLA' proteins.
(a) The Le-1 gene codes for the enzyme GA20 oxidase. A mutation of this gene forms a recessive allele which, when translated, leads to a single amino acid change in this enzyme. This change significantly reduces the activity of GA20 oxidase.
Explain how a single amino acid change can bring about a change in the structure and activity of GA20 oxidase.
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(b) (i) Explain why homozygous recessive plants will have short stems.
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(ii) An ecological survey of a stable population of one species of plant found that 36% had short stems.
Calculate the percentage of heterozygous individuals in this population. Assume that there are only two alleles for this gene.
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(Total for question = 12 marks)
Q16.
The photograph shows the hand of a person with the inherited condition 'WHIM'.
This condition results in a defective immune system, warts on the skin surface and an increased risk of cancer.
A woman had WHIM but her symptoms disappeared. However, she was worried that she had passed the condition on to her children.
Bone marrow is responsible for making white blood cells.
Scientists found that the woman had a single mutation in a bone marrow stem cell. This caused 'chromosome shattering' with the loss of 164 genes, including the defective gene.
(i) Explain how this mutation in a bone marrow stem cell had cured her of WHIM.
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(ii) Some people have complained about the use of stem cells from fetal cell lines in the development of Ebola vaccines.
Explain why these stem cells are being used to produce vaccines rather than bone marrow cells.
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Q17.
The scientific article you have studied is adapted from articles in Nature and ScientificAmerican.
Use the information from the article and your own knowledge to answer the question.
* Suggest how researchers had genetically modified the pathogen to 'provoke an effective immune response' (paragraph 12).
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Q18.
Scientists are developing ways of using stem cells to replace heart cells that have been damaged as a result of heart disease.
Both embryonic stem cells and induced pluripotent stem cells (iPS cells) can be used to create new heart cells.
Compare and contrast the properties and uses of embryonic stem cells with those of iPS cells.
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(Total for question = 5 marks)
Q19.
In February 2016, the World Health Organisation (WHO) declared a public health emergency because of the spread of the Zika virus.
The mild symptoms, such as joint pains, headaches and a slight temperature increase lasted only a few days. However, Zika virus has been linked to a birth defect called microcephaly.
The graph shows the number of babies born with microcephaly in Brazil from 2010 to 2015.
Zika virus is transmitted to humans by infected mosquitoes.
(i) Explain why another type of drug, rather than antibiotics, has to be used to treat Zika virus infections.
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(ii) Scientists have suggested that genetically modified (GM) mosquitoes could be used to help combat the spread of the Zika virus.
Mosquito eggs are injected with DNA, from GM mosquitoes. This DNA contains a gene for fluorescence. However, only one in a few thousand injected eggs results in a GM mosquito.Explain how this procedure could help in the production of large numbers of GM mosquitoes.
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(iii) Explain why the Brazilian government has advised people to use mosquito nets, even if they have already contracted the Zika virus.
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(Total for question = 8 marks)
Q20.
The scientific article you have studied is adapted from articles in Nature and ScientificAmerican.
Use the information from the article and your own knowledge to answer the question.
'While the manipulated individual may look like an ant, it represents a fungal genome expressing fungal behaviour through the body of an ant' (paragraph 33).
Suggest how fungal genes may be expressed and affect the behaviour of these ants.
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Q21.
Monoclonal antibodies can be made against a wide range of different antigens. They are used in research and medicine.
Monoclonal antibodies are made by fusing an antibody-producing cell with a myeloma cell.
The diagram shows some of the steps involved in making monoclonal antibodies against human cancer cell antigens.
Myeloma cells have the potential to divide indefinitely.
Explain why myeloma cells are used in the production of monoclonal antibodies.
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(Total for question = 2 marks)
