O-LevelBiologyCoordination & Response5090/21 · May/June 2018 · Q59 Marks

No introductory text, directly to part (a).

(a)(i)Describe the main characteristics of a virus.[3]
(a)(ii)The human immunodeficiency virus (HIV) reproduces inside white blood cells and destroys them. Use your knowledge of the functions of white blood cells to suggest why the virus is named the immunodeficiency virus.[2]
(b)(i)HIV causes a disease called AIDS. The virus may be transmitted during sexual intercourse. State two methods by which the spread of HIV by sexual intercourse may be controlled. 1 2[2]
(b)(ii)HIV may be transmitted in other ways. State two ways, other than during sexual intercourse, by which HIV may be transmitted. 1 2[2]

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

[3] very AW small; protein coat/capsid; no membrane / no cytoplasm / no nucleus / non-cellular / no organelles ; nucleic acid / DNA/RNA ; parasitic/ (may be) pathogen(ic) / cause disease / non-living AW ; unaffected by antibiotics;
[2] reference to immune / immunity (system or affected) ; reference to reduced AW + antibody production ; reference to reduced AW + phagocytic action;
[2] barrier contraception / correct named contraceptive method e.g. condom ; abstinence; only one partner AW ; reference to use of anti-retroviral drugs ; A avoid unprotected sex
[2] sharing + needles / sharp objects / toothbrushes ; blood transfusion / contact ; from mother to baby / across placenta / during birth / during breast-feeding ;

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