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

Date	May 2017	Marks available	2	Reference code	17M.3.SL.TZ1.16
Level	Standard level	Paper	Paper 3	Time zone	Time zone 1
Command term	Calculate	Question number	16	Adapted from	N/A

Question

Freshwater invertebrates were sampled by students at three sites along a river in central France. The animals were identified and counted. The diversity of each site can be compared using Simpson’s reciprocal index.

Simpson’s reciprocal index is given by the following formula:

Calculate the diversity of site C. Working should be shown.

[2]

Site A has a higher Simpson’s reciprocal index than Site B showing that its diversity is higher.

Explain the reason that ecologists consider Site A to have a higher diversity than Site B, despite both sites having six different species present.

[2]

Discuss the advantages and disadvantages of in situ conservation methods.

[4]

Markscheme

b. = 3.56 «allow 3.55»

a. the species in Site A are more evenly represented than site B

b. site B has a large number of one species «but very few in the other 5»

c. Simpson’s reciprocal index is a measure of species evenness as well as species richness

Advantages:
a. conservation in the natural habitat / ecosystem

b. the species will have all the resources that it is adapted to

c. the species will continue to evolve in their environment / can maintain genetic diversity

d. the species have more space so a bigger breeding populations can be kept

e. it is cheaper to keep an organism in its natural habitat

f. established food webs/ species interactions can be maintained

Disadvantages:

g. it is difficult to control illegal exploitation «eg poaching»/harder to monitor populations

h. the area may need restoring / may be required for other purposes

i. alien species are difficult to control

j. species close to extinction are harder to conserve

k. management/protection may represent a significant cost

Date	May 2015	Marks available	2	Reference code	15M.3.SL.TZ2.17
Level	Standard level	Paper	Paper 3	Time zone	Time zone 2
Command term	Outline	Question number	17	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 2015	Marks available	1	Reference code	15M.3.SL.TZ1.18
Level	Standard level	Paper	Paper 3	Time zone	Time zone 1
Command term	Identify	Question number	18	Adapted from	N/A

Question

Identify one risk associated with gene therapy.

Markscheme

a. stimulate autoimmune response/tissue rejection / infection resulting from vector;
b. cancer/oncogenes / overexpression of gene;
Do not accept death as a response

Date	November 2015	Marks available	1	Reference code	15N.3.SL.TZ0.16
Level	Standard level	Paper	Paper 3	Time zone	TZ0
Command term	State	Question number	16	Adapted from	N/A

Question

Data on microbial resistance to the fluoroquinolone family of antibiotics was collected in US hospitals. The graph shows the relationship between Pseudomonas aeruginosa, other Gram-negative bacteria and the use of fluoroquinolone from 1993 to 2000.

State the percentage of P. aeruginosa that were resistant to fluoroquinolone in 1996.

[1]

Compare the trends in fluoroquinolone use and resistance to fluoroquinolone in other Gram-negative bacteria between 1993 and 2000.

[2]

Predict the results if data from the same hospitals were collected for P. aeruginosa resistance in 2001.

[1]

Discuss the implications of the data in the graph for the health of patients.

[3]

Markscheme

23 (%)

Accept answer in the range of 22(%) to 24 (%).

a. positive correlation / other Gram-negative bacteria resistance increases as fluoroquinolone use increases;

b. other Gram-negative bacteria continues to increase / slight decrease of fluoroquinolone use (in 1997);

c. from 1998, other Gram-negative bacteria resistance continues to rise even though fluoroquinolone use starts to level off/decreases;

P. aeruginosa resistance would increase (slightly)/level off

a. there is rising incidence of antibiotic/fluoroquinolone-resistant P. aeruginosa/ other Gram-negative bacteria;

b. use of antibiotics/fluoroquinolone is increasing/becoming less effective;

c. careful use of antibiotics/fluoroquinolone is recommended;

d. other antibiotics (that do not promote resistance) need to be developed;

e. continued monitoring of the situation is needed;

f. less chance of treating the disease / more severe symptoms / more people with the disease;

Date	November 2015	Marks available	4	Reference code	15N.3.SL.TZ0.18
Level	Standard level	Paper	Paper 3	Time zone	TZ0
Command term	Discuss	Question number	18	Adapted from	N/A

Question

Researchers are studying several ways to treat cancer using gene therapy.

Discuss the risks of gene therapy.

Markscheme

a. virus vector might infect another cell by mistake;

b. (virus vector) might place the new gene in the wrong section of DNA/cause cancer/mutation;

c. genes may be over-expressed/make too much protein which may be harmful;

d. (virus vector) might stimulate an immune reaction;

e. (virus vector) might be transferred from person to person;

f. children might be more sensitive to long-term hazards since their tissues are still developing;

Date	May 2013	Marks available	2	Reference code	13M.3.SL.TZ2.17
Level	Standard level	Paper	Paper 3	Time zone	Time zone 2
Command term	Discuss	Question number	17	Adapted from	N/A

Question

Explain how Gram staining is used in microbiology.

[3]

Discuss the possible consequences of gene therapy.

[2]

Markscheme

a. Gram staining is used to classify bacteria/Eubacteria;
b. cell wall structure determines how Gram stain is received;
c. bacteria termed as Gram-positive or Gram-negative;
d. Gram-positive bacteria appear purple;
e. Gram-negative bacteria (stain less intensely and) appear pink/red;

most attempts have been unsuccessful/caused harm or death/caused emotional trauma/conflicts of interest/ethical issues;
might alleviate (genetic) condition / correct a (genetic) defect;

Date	May 2011	Marks available	3	Reference code	11M.3.SL.TZ1.18
Level	Standard level	Paper	Paper 3	Time zone	Time zone 1
Command term	Discuss	Question number	18	Adapted from	N/A

Question

Discuss the risks of gene therapy.

Markscheme

at present, gene therapy treatment effects may be short-lived / process may need to be repeated/fails;
reintroduction of cells/introduction of viral vector to the patient risks immune response;
viral vectors may infect the patient;
insertion of DNA may lead to tumours;

Date	May 2011	Marks available	3	Reference code	11M.3.SL.TZ2.17
Level	Standard level	Paper	Paper 3	Time zone	Time zone 2
Command term	Describe	Question number	17	Adapted from	N/A

Question

Describe the use of viral vectors in gene therapy.

Markscheme

gene therapy involves replacing defective genes;
desired gene is inserted into the viral genome;
viruses can be modified to infect only target cells and not self-replicate / modified for safe use;
somatic cells are removed (for receiving the new genes);
the desired gene is introduced into the target/somatic cells;
altered cells are returned to the patient for expression of the gene;
properly described verified example e.g. replacement of gene for production of ADA in SCID / introduction of gene/RPE65 (in retina) to restore vision in inherited blindness (LCA) / replacement of factor IX/blood clotting factor gene in hemophilic patients;

Date	May 2012	Marks available	2	Reference code	12M.3.SL.TZ1.18
Level	Standard level	Paper	Paper 3	Time zone	Time zone 1
Command term	Outline	Question number	18	Adapted from	N/A

Question

Gene therapy is a new technology which can be used to treat hereditary diseases.

Outline two risks of gene therapy.

Markscheme

undesired effects e.g. cancer/death;
virus may infect cells other than the target cells;
inserted gene may disrupt vital genes already in the genome;
virus entry may trigger an immune response;
treatment must be repeated at regular intervals and all medical treatments carry risk;

Date	May 2010	Marks available	3	Reference code	10M.3.SL.TZ2.18
Level	Standard level	Paper	Paper 3	Time zone	Time zone 2
Command term	Discuss	Question number	18	Adapted from	N/A

Question

Gene therapy may offer cures for inherited diseases and, perhaps, improve quality of life. Distinguish between somatic and germ line therapy.

[2]

Discuss risks of gene therapy.

[3]

Markscheme

somatic (gene therapy) involves changes to body cells whereas germ line (gene therapy) involves changes to egg cells/gametes;
somatic cell changes are not passed on to offspring whereas germ line changes may be passed on to offspring;
somatic cell genes affect only a small proportion of the total cells in a body whereas the changes to germ line cells will be passed on to all cells of the offspring (as it develops);

prevents/reduces symptoms of a disease so taking the risk is worthwhile;
immune response to the vector may cause damage to the recipient;
long-term effects to the patient are unknown;
impact on offspring of the treated person is unknown;
risk of “designer babies” which poses risks to social norms;
risk of consent during research trials being uninformed / other reasonable answer about research trials;

Date	November 2011	Marks available	2	Reference code	11N.3.SL.TZ0.17
Level	Standard level	Paper	Paper 3	Time zone	TZ0
Command term	Outline	Question number	17	Adapted from	N/A

Question

Outline the use of viral vectors in gene therapy.

Markscheme

viral vector used to replace defective gene in somatic cell;
virus genetically engineered to carry normal copy of gene;
normal gene expressed in body cells;
valid example; (e.g. used to treat severe combined immune deficiency disease (SCID));

Date	November 2009	Marks available	3	Reference code	09N.3.SL.TZ0.17
Level	Standard level	Paper	Paper 3	Time zone	TZ0
Command term	Outline	Question number	17	Adapted from	N/A

Question

The electron micrograph below shows a pathogen.

Identify the type of pathogen shown in the electron micrograph, giving reasons for your answer.

[2]

Outline the use of viral vectors in gene therapy.

[3]

Markscheme

virus;

protein coat;

RNA/riboprotein;

removal of white blood cells / bone marrow cells;

using a vector; insert gene into chromosome;

cells are replaced in the body of the patient;

the normal gene can be expressed;

e.g. SCID where the replaced gene allows for the production of ADA/Adenosine deaminase;