| Date | May 2018 | Marks available | 8 | Reference code | 18M.2.SL.TZ2.6 |
| Level | Standard level | Paper | Paper 2 | Time zone | Time zone 2 |
| Command term | Explain | Question number | 6 | Adapted from | N/A |
Question
Although simple in structure, bacteria as a group show a wide range of diversity.
Outline the roles bacteria play in the carbon cycle.
Describe the evolution of antibiotic resistance in bacteria.
Explain the process of genetically modifying bacteria.
Markscheme
a. decomposition of dead organic material «by saprotrophic bacteria»
b. «decomposition» leads to CO2 formation/regeneration due to respiration
c. «saprotrophic bacteria only» partially decompose dead organic matter in acidic/anaerobic conditions in waterlogged soil
d. results in peat formation in bogs/swamps
e. photosynthetic bacteria/cyanobacteria fix CO2 in photosynthesis
a. problem results from excessive use of antibiotics by doctors/veterinarians/in livestock
OR
low antibiotic doses taken by patients (not finishing treatment)
b. natural variation exists in any population of bacteria making some resistant to a specific antibiotic
c. variation arises from mutation
OR
antibiotic resistance can be transferred between bacteria by plasmids
d. antibiotic kills all bacteria except those that are resistant
e. resistant bacteria survive, reproduce and pass on resistance to offspring
f. soon population is made of mainly antibiotic resistant bacteria
g. this is an example of natural selection «increasing frequency of characteristics that make individuals better adapted to environment»
a. genetic modification carried out by gene transfer between species
b. genes transferred from one organism to another produce the same protein/amino acid sequence
c. due to universality of genetic code
OR
organisms use same codons of mRNA to code for specific amino acids
d. mRNA for required gene extracted/identified
e. DNA copies of mRNA made using reverse transcriptase
f. PCR used (to amplify DNA to be transferred)
g. genes/DNA transferred from one species to another using a vector
h. plasmid acts as vector to transfer genes to bacteria/E. coli
i. plasmid cut open at specific base sequences using restriction endonuclease
OR
plasmid cut to produce blunt ends then extra cytosine/C nucleotides added
OR
sticky ends made by adding extra guanine/G nucleotides
OR
mention of sticky ends if not gained already
j. cut plasmids mixed with DNA copies stick together (due to complementary base pairing)
k. DNA ligase makes sugar-phosphate bonds to link nucleotides of gene with those of plasmid
l. bacteria that take up plasmid are identified
m. (genetically modified) bacteria will reproduce carrying the transferred gene
n. example – eg: as production of human insulin using E. coli bacteria
Accept any of the points clearly explained in an annotated diagram.
Examiners report
Syllabus sections
-
19M.2.SL.TZ2.1i:
Outline the conclusions that can be drawn from the data in the graph for the group of aphids fed for three generations on transgenic thale cress plants (T).
- 17N.2.SL.TZ0.02c: State an application of plasmids in biotechnology.
- 18M.1.SL.TZ2.16: Which technique is used to amplify very small samples of DNA? A. Cloning B. Gel...
- 18M.1.HL.TZ2.19: Which technique is used to amplify very small samples of DNA? A. Cloning B. Gel...
- 17M.1.HL.TZ2.21: Which is a possible risk associated with a genetic modification of crops? A. Crop plants...
- 17N.2.SL.TZ0.06c: Outline natural methods of cloning in some eukaryotes.
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18N.1.SL.TZ0.16:
The image shows the results of Griffith’s experiment with S and R strains of Streptococcus pneumoniae in mice (Mus musculus).
What is an explanation for the results?
A. Mice vary in their resistance to bacteria.
B. The R strain and S strain mated.
C. R strain bacteria are more heat-stable than S strain.
D. DNA was transferred from heat-killed S cells to R cells.
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21N.1.HL.TZ1.13:
A nucleus was removed from a cell of sheep P and fused with a denucleated egg cell of sheep Q. This was transplanted into the uterus of sheep R, which gave birth to Dolly.
[Source: Photo courtesy of The Roslin Institute, The University of Edinburgh, Roslin, Scotland, UK, n.d. Dolly the Sheep
in a field at The Roslin Institute. [image online] Available at: https://www.livescience.com/57961-dolly-the-sheepannouncement-
20-year-anniversary.html [Accessed 23 March 2020].]Which describes Dolly?
A. A clone of sheep P, because Dolly was formed from the nucleus of its udder cell
B. A clone of sheep Q, because Dolly was formed from one of its egg cells
C. A clone of sheep R, because Dolly developed in its uterus
D. Not a proper clone, as more than one sheep was involved in the development
- 16N.1.SL.TZ0.13: What is produced by somatic-cell nuclear transfer? A. Adult sheepB. Cloned embryosC. Rooted...
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18N.1.HL.TZ0.14:
Ampicillin (Amp) is an antibiotic. A plasmid carrying a gene for Amp resistance was used to transform bacteria in a tube of broth. A control tube without plasmid was also produced. The results were plated as shown. Which plate has only colonies of transformed bacteria?
- 21N.1.SL.TZ0.16: The image shows the result of DNA profiling of a mother, a child and four men. Which man is...
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19M.1.HL.TZ2.22:
Two restriction endonucleases (EcoRI and BamHI) were used to cut a DNA sample into smaller fragments. These were then subjected to gel electrophoresis and the results are shown. The lengths of the DNA fragments are measured in kilobases (kb). One kilobase is 1000 DNA bases.
[Source: © International Baccalaureate Organization 2019]
Which statement is supported by the data?
A. The DNA sample is approximately 16 kb in size.
B. Each endonuclease produces a 2 kb fragment.
C. Both endonucleases produce the same number of fragments.
D. The fragments produced using both endonucleases are all different from those produced by the individual endonucleases.
- 19M.2.HL.TZ2.1f: Using the gene activation data, deduce, giving two reasons, whether the armyworm or the...
- 17N.1.SL.TZ0.15: HindIII is an endonuclease that recognizes the sequence A A G C T T, cutting between the two...
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
- 19N.1.SL.TZ0.17: What is PCR used for? A. Separate fragments of DNA by size B. Amplify small amounts of...
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
-
22M.2.HL.TZ1.8b:
Describe how DNA profiling can be used to establish paternity.
-
22M.2.SL.TZ2.7c:
Suggest possible benefits and risks of using genetic modification to develop varieties of crop plant with traits such as drought resistance.
-
20N.1.HL.TZ0.12:
In DNA profiling, short tandem repeats (STRs) of DNA are used, as these vary a great deal between individuals. Some skin cells were retrieved from a crime scene. Three STR sections of the DNA from these cells, from the victim and from a suspect, were analysed and the results are shown in the table.
What can be concluded from the gel electrophoresis data?
A. The suspect was at the crime scene.
B. The victim has the band moving the least distance.
C. The suspect and the victim have bands moving the same distance.
D. The skin cells have the band moving the greatest distance.
-
22M.1.SL.TZ2.16:
A cloning method used for livestock involves in vitro fertilization (IVF) with selected male and female gametes. The diagram shows the steps followed after in vitro fertilization.
[Source: Aldona Griskeviciene / Shutterstock.com.]
What does X represent?
A. A group of eggs
B. An embryo
C. A follicle
D. A group of zygotes
- 19M.2.HL.TZ2.1c: Identify the process that was used to amplify the targeted genes.
- 19M.2.HL.TZ2.1d: Deduce, with a reason, which gene is first transcribed when exposed to C2.
- 21M.1.SL.TZ2.16: What benefit is derived from the use of Bt crops? A. It can lead to an increase in genetic...
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
- 17M.2.HL.TZ1.1e: Outline the additional evidence provided by the gel electrophoresis results shown above.
-
17M.2.SL.TZ1.5c:
Explain benefits and risks of using genetically modified crops for the environment and also for human health.
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
- 19M.2.SL.TZ2.1h: Identify, with a reason, the aphids that were most strongly repelled by EBF.
- 18N.1.HL.TZ0.27: Sanger developed a method for determining DNA base sequences using terminating nucleotides...
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20N.2.HL.TZ0.8c:
Discuss the process, including potential risks and benefits, of using bacteria to genetically modify plant crop species.
- 19M.2.SL.TZ2.1j: Discuss whether natural selection would favour the transgenic EBF-producing thale cress...
- 19M.2.HL.TZ2.1b: Compare and contrast the effects of treatment of the leaves using C1 and C2 with the effects...
- 19M.2.HL.TZ2.1a: Distinguish between the data for the leaves infested with the armyworm and the leaves...
-
19M.1.SL.TZ2.16:
Genetically modified maize, called Bt maize, is thought to be affecting the monarch butterfly (Danaus plexippus) in the USA. What is the reason for this?
A. The monarch butterfly feeds on maize nectar, which contains Bt toxin.
B. The monarch caterpillar feeds on maize leaves, which contain Bt toxin.
C. Bt toxin kills the plants that the monarch caterpillar usually eats.
D. Bt toxin is in maize pollen, which blows on to plants that the monarch caterpillar eats.
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19M.2.HL.TZ2.1e:
Each gene is activated by one or more of the treatments. From the gel electrophoresis data, discuss the impact of the herbivorous mite infestation on gene activation compared to treatment with C1 and C2.
-
21M.2.HL.TZ1.8a:
Outline the process of DNA profiling.
- 17M.1.HL.TZ1.26: A DNA profile was made of one individual in a paternity suit. Locus B was used to distinguish...
