SL Biology  6.3  Questions on HIV from past papers ANSWERS
1.	(a)	I: protein coat / capsid / capsomere;
II: DNA / nucleic acid / RNA / genetic material;	2
 
(b)	
	52 nm (±5 nm); (units required)	2
 
(c)	antibiotics block specific metabolic pathways / 
cell production in bacteria;
viruses reproduce using the host cell metabolic pathways;
(host cell) pathways are not affected by antibiotics;
viruses do not have metabolic pathways;	3 max
 
(d)	some bacteria are resistant to an antibiotic / 
variation within bacterial populations includes antibiotic resistance;
genes for antibiotic resistance originate as
mutations (not caused by antibiotics);
transfer of resistance genes (can occur) from strain to strain / 
species to species;
bacteria that are resistant survive when an antibiotic is used and others die;
resistant bacteria pass on their genes for resistance to offspring;
proportion of resistant bacteria increases in each
generation in the population / species;
natural selection for bacteria that are resistant;	3 max
[10]

2.	Responses must include reference to cause, transmission and social implications 
to receive full marks.
	cause:
human immunodeficiency virus / HIV / HIV 1 and HIV 2;
retrovirus / RNA to DNA;
enters T-helper cells;
immune system becomes disabled / weakened;
greater chance for opportunistic infections;
 
	transmission:
sexually transmitted;
can be transmitted from man to woman / man to man contact / woman to man / 
mother to fetus;
breast milk / saliva and other body fluids;
use of dirty needles;
blood transfusions;

	social implications of AIDS:
many orphaned children;
social stigma / discrimination;
problems obtaining employment / life insurance;
impact / costs on health systems of treating people;
early death reduces number of adults / reduces workforce / reduces family income;
drug treatment expensive;
reduces promiscuity / encourages use of condoms;	8 max
(Plus up to [2] for quality)
[8]

3.	(a)	(i)	1967	1
(ii)	(death rate = 5 per 100,000 / yr, total number of deaths would be 5
times 198 =) 990 deaths	1
 
(b)	death rate in Canada is always lower than United Kingdom;
	highest death rate in United Kingdom approx 40 per 100,000 whereas in
Canada never above 15;
no death from influenza recorded in Canada in 1957 but some in the
United Kingdom;
	highest death rate for United Kingdom recorded in 1953 but in Canada
in 1958;
both countries have very low / zero death in 1954 and 1957;
between 1953 to 1963 patterns are very similar;	3 max
 
(c)	viruses consist of nucleic acid and a protein coat;
DNA double stranded or single stranded;
RNA double stranded or single stranded;
protein coat contains receptors specific for target organism;	2 max
[7]