IB DP Biology Option B: Biotechnology and bioinformatics (AHL topics) :B.4 Medicine HL Paper 3

Date	November 2017	Marks available	6	Reference code	17N.3.HL.TZ0.13
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Discuss	Question number	13	Adapted from	N/A

Question

Discuss biopharming.

Markscheme

a. produces useful pharmaceuticals/drugs/proteins

b. inserts genetic material/genes into host plants/animals

c. produces more complex drugs/proteins than prokaryotic organisms

no post-translation modification with prokaryotes «so no complex proteins»

d. valid example

Allow verifiable examples, eg: antithrombin/coagulation factors «in goats», development of Norwalk virus/
cholera toxin vaccines «in tomatoes»

e. issues regarding contamination of other organisms

possible ecological effects

f. plants process proteins differently than humans

g. proteins produced by plants may cause allergic reaction

h. some proteins are intellectual property

i. example of ethical issue

[Max 6 Marks]

Date	November 2017	Marks available	1	Reference code	17N.3.HL.TZ0.10
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Outline	Question number	10	Adapted from	N/A

Question

The table shows a comparison of DNA base sequences in several yeast (Saccharomyces) genomes.

[Source: P. F. Cliften et al. (2001) ‘Surveying Saccharomyces Genomes to Identify Functional Elements by Comparative DNA Sequence Analysis’, Genome Research, 11, pp. 1175–1186. © Cold Spring Harbor Laboratory Press. Reproduced with permission.]

Identify the species that has the lowest percentage of coding sequences.

[1]

State how similar nucleotide sequences can be identified.

[1]

The yeast Saccharomyces cerevisiae was the first eukaryotic organism to have its entire genome sequenced. Suggest reasons for the choice of yeast as a study organism.

[3]

Outline possible medical applications of the polymerase chain reaction (PCR).

[1]

Markscheme

S. unisporus

BLASTn/sequence alignment software

“n” required in BLASTn

a. easy to grow

easy/cheap to produce large amounts

fast generation time

b. genomes are small/easy to manipulate

c. metabolically diverse

d. industrial applications/biopharming

e. no ethical issues «with yeast»

[Max 3 Marks]

a. identify different viral/influenza strains

b. genetic testing/testing for genetic disease mutations

c. tissue typing

d. vaccine development

[Max 1 Mark]

Date	May 2017	Marks available	2	Reference code	17M.3.HL.TZ2.12
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	Outline	Question number	12	Adapted from	N/A

Question

Outline one way in which genetic sequences can be used to indicate predisposition to a disease.

[3]

Outline the use of luminescent probes in the treatment of tumours.

[2]

Markscheme

a. genetic markers/specific sequences can be present in people with a disease OWTTE

b. presence «of markers/specific sequences» indicates risk/probability of onset of condition Allow vice versa.

c. technique to detect the presence of the sequence eg: PCR, electrophoresis, DNA sequencing, FISH, DNA databases, etc.

d. example of predisposition eg: BRCA sequence mutations indicating predisposition to breast cancer

a. transferrin/other protein taken up at higher rates by tumour cells

b. transferrin/other protein can be labelled with a luminescent dye

c. different tumour cell types can be distinguished/labelled in different colours

d. can be used to highlight tumours «during surgery» OWTTE

Date	May 2017	Marks available	3	Reference code	17M.3.HL.TZ1.11
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Outline	Question number	11	Adapted from	N/A

Question

Outline what is meant by the term genetic markers.

[1]

a.i.

Outline two uses of genetic markers.

[2]

a.ii.

Evaluate the use of viral vectors in gene therapy.

[2]

Outline the use of microarrays to test for genetic disease.

[3]

Markscheme

A gene/DNA sequence «with a known location on chromosome» used for identification

a.i.

a. to identify species/pathogenic organisms
OR
successful uptake of DNA in genetically modified organisms/GMOs

b. to detect disease due to variation in DNA «substitution/deletion»

c. to determine risk of developing certain disorders

d. to confer resistance to antibiotic/agent that would normally kill it

e. to make cells containing gene look different
OR
green fluorescent tag makes cells visible under UV light

a.ii.

a. gene therapy trials have used viruses to deliver un-mutated copies of genes to the «somatic» cells of the patient’s body

b. examples of the use of viral vectors eg gene therapy may provide a way to cure genetic disorders, such as severe combined immunodeficiency

c. one of the main problems is immune response to viruses / may cause toxicity/disease

d. some viral vectors insert their genomes at a random location on one of the host chromosomes «which can disturb the function of cellular gene» / enter wrong cells «if targeting tumour» / could lead to cancer

a. analyze tissue/blood sample for DNA sequence

b. each spot «on microarray» has small quantity of specific DNA sequence/probe

c. reverse transcriptase used to make cDNA

d. fluorescent dye linked to cDNA

e. «cDNA» binds to/hybridizes with probes that have complementary base sequences

f. fluorescence/different colours shows probes have hybridized / which sequences were in the tissue sample

Allow specific examples of genetic diseases.

Date	November 2016	Marks available	4	Reference code	16N.3.HL.TZ0.11
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Discuss	Question number	11	Adapted from	N/A

Question

Metabolites that indicate disease can be detected in urine. State a metabolite found in urine and the disease it could indicate.

[2]

Discuss the implications of biopharming using a specific example.

[4]

Markscheme

a. named metabolite

eg: glucose

b. associated disease

eg: diabetes

a. production of pharmaceuticals
OR
named example of biopharming

b. easily scaled to cover demands
OR
cheaper

c. drugs can be delivered in food «making it more attractive/easier to eat»

d. unethical/ethical aspect/OWTTE

e. allergic reactions/ side effects

f. horizontal gene transfer consideration

Date	May 2016	Marks available	6	Reference code	16M.3.HL.TZ0.13
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Explain	Question number	13	Adapted from	N/A

Question

Explain how infection by a pathogen can be detected by an ELISA test for antigens.

Markscheme

Infected individual will have pathogens/antigens in bodily fluids

Test contains immobilized/fixed antibodies to the pathogen/antigen

If present, antigen binds to «immobilized» antibody/capture molecule

Solution is washed and only fixed antigen-antibody complexes persist

Then a detection antibody linked to an enzyme is added

Reacts with fixed antigen-antibody complex

A chromogenic/potentially fluorescent substance is added

Enzyme changes substance to a different/detectable colour

The presence of colour is a positive response/absence of colour a negative response

Date	May 2015	Marks available	1	Reference code	15M.3.HL.TZ1.7
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Identify	Question number	7	Adapted from	N/A

Question

Over a thousand bacterial species occupy the human gut. The gut bacteria show much larger genetic diversity than the host cells. Gut bacteria are vital to proper food digestion and vitamin synthesis. Fecal samples were collected from people in various locations so the genomes of their gut bacteria could be analysed. Bacteria with the same unique DNA sequences were identified as species. The graph shows the number of bacterial species in the digestive tract of people in three different parts of the world.

Identify the age and ethnic group of the individual with the highest diversity of gut bacterial species.

[1]

Outline the trends in the number of bacterial species in the digestive tracts of Amerindians.

[1]

b (i).

Distinguish between the trends seen in the three populations.

[2]

b (ii).

Suggest two reasons for how the different environments of the three human populations affect the number of bacterial species in their digestive tracts after the age of four.

[2]

A century ago, it was discovered that each person belonged to one of four blood types. Now some researchers are reporting that human gut ecosystems fall into three distinct types, each involving a great number of similar bacterial species.

Suggest one medical application based on the knowledge that humans could be typed according to their gut ecosystem.

[1]

Markscheme

34 (years old) and Amerindian
Allow answers in the range 33–35.

a. rapid increase in diversity early in life/before age four;
b. (from age four into adulthood) bacterial diversity tends to level off/stay within same (broad) range of diversity/great variation;

b (i).

a. Amerindians reach highest plateau / Malawians and US reach a lower plateau than the Amerindians;
b. US reach lowest plateau / US reach a lower plateau than the Malawians and Amerindians;

b (ii).

a. US population use disinfectants/antiseptics / pasteurise/sterilise/irradiate food more than populations in Malawi or Amazon;
b. different diets support different populations of bacteria;
c. different soil/water/local animal bacteria;
d. different use of antibiotics;
e. contact with farm/wild animals by rural populations;

a. diets could be tailored to a particular gut ecosystem to maximize digestion / personal health/weight control;
b. antibiotics could be prescribed with minimal effect on gut bacteria/reduce diarrhoea;
c. fecal transplants; (accept other reasonable answers)

Date	May 2015	Marks available	2	Reference code	15M.3.HL.TZ2.8
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	Outline	Question number	8	Adapted from	N/A

Question

Outline how a defective gene can be replaced using viral vectors.

Markscheme

a. viral vector modified to include healthy gene;
b. virus is taken up by cells;
c. inserts normal gene into chromosome;
d. white blood cells / bone marrow/other cells replaced into patient;

Date	May 2010	Marks available	6	Reference code	10M.3.HL.TZ1.9
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Discuss	Question number	9	Adapted from	N/A

Question

Discuss methods used in gene therapy, including the risks involved.

Markscheme

somatic cell therapy methods alter the genetic material of somatic cells/nongametes;
could cure the individual treated but disease can still be passed to offspring;
germ-line therapy methods alter the genetic material of sex-cells/gametes/sperm/eggs;
disease would be absent in future offspring;
retroviruses/viruses are used (as vectors);
to insert (normal) gene/allele (in host cells);
verified application, e.g. treatment of SCID (severe combined immunodeficiency);
no fully successful cases since relatively new / technical issues need to be solved e.g. ensure correct amount of gene product/at the right time/in the right place;
cases of gene therapy causing cancer in patients / infect healthy cells causing illness / harm other cell functions / e.g. (two) children treated for SCID developed leukaemia;
immune system may attack newly introduced viruses causing inflammation/toxicity/organ failure;

Date	November 2011	Marks available	6	Reference code	11N.3.HL.TZ0.9
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Discuss	Question number	9	Adapted from	N/A

Question

Discuss the use of viral vectors in gene therapy including the risks involved.

Markscheme

viral vector used to replace defective gene in somatic cell;
virus genetically engineered to carry normal copy of gene;
valid example; (e.g. SCID (severe combined immunodeficiency))
cause of disease; (e.g. lack of enzyme/adenosine deaminase/ADA in bone marrow cells)
technical issues need to be solved / ensure correct amount of gene product/at the right time/in the right place;
need to be sure insertion of therapeutic gene does not harm other necessary cell functions;
viral vectors may infect healthy cells;
causing illness/disease/cancer;
virus may revert to original form and cause disease;
newly introduced DNA may affect reproductive cells causing genetic changes;
immune system may attack newly introduced viruses causing inflammation/toxicity/ organ failure;

Date	November 2009	Marks available	6	Reference code	09N.3.HL.TZ0.9
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Discuss	Question number	9	Adapted from	N/A

Question

Discuss the risks of gene therapy including safety, conflict of interest and ethical arguments.

Markscheme

definition:

insertion of genes / replacement of defective genes using a vector into non-germ line cells;

safety:

the DNA/viral vector may integrate into other parts of the genome;

causing problems of gene expression;

possibly cancer;

example of SCID treatment/leukemia;

the vector may trigger an immune response;

viral vectors may recombine with other viruses;

inadvertent modification of germ line cells;

conflict of interest:

the producers of gene vectors gain financially;

clinical trials must be free of bias from commercial sponsors;

ethics:

the vectors are tested on animals and may behave differently in humans;

unethical to use healthy humans in trials;

no gene therapy has been commercialized / no valuable results as yet;

Award [4 max] if responses do not address safety, conflict of interest and ethics.