| Date | November 2009 | Marks available | 2 | Reference code | 09N.2.HL.TZ0.2 |
| Level | Higher level | Paper | Paper 2 | Time zone | TZ0 |
| Command term | Outline | Question number | 2 | Adapted from | N/A |
Question
HIV was discovered in 1981 and is now one of the most serious causes of disease in the world. It causes the immune system to fail, leaving the patient vulnerable to other infections.
Outline how monoclonal antibodies are produced.
Discuss how the HIV virus is transmitted.
Explain why antibiotics are ineffective against viruses.
Markscheme
B lymphocytes are produced in laboratory animal after injection with an antigen;
animal cells/these cells are fused with tumour cells (to form hybridomas which) produce antibodies;
HIV virus transmitted by body secretions/semen/blood/across placenta;
transmitted by infected blood transfusions/intravenous drug users;
mainly by sexual activity/promiscuity;
antibiotics block metabolic pathways / work only on bacteria;
viruses reproduce using their hosts’ metabolic pathways / do not have their own metabolic pathways;
Examiners report
The topic of monoclonal antibodies was not well known by the candidates of many centres. Well prepared candidates gained the two marks, although some lost a mark for fusing antibodies rather than B lymphocytes with the tumor cell.
With some very weak candidates this part gave them nearly all of their marks.
As with part b, some candidates did not know why antibiotics are ineffective against viruses.
