B1 H - Sample set 1 Q10
10) There are different types of white blood cell in the body. One type is called CD4+ T-Helper cells.
The normal range of these cells in the blood is between 5×108 and 1.2×109 cells/dm3
An AIDS patient has a CD4+ T-Helper cell count of 1.5×108 cells/dm3
(a) Explain why the CD4+ count of 1.5×108 cells/dm3 has led to the diagnosis of AIDS. (2)
*(b) Some sexually transmitted infections (STIs) can be diagnosed by testing urine samples.
These tests use monoclonal antibodies that bind to an antigen on the pathogen.
Describe how a monoclonal antibody can be developed and used to detect an STI using a urine sample. (6)
(c) The antigens on pathogens can be proteins with a specific amino acid sequence.
Explain how the order of amino acids in a protein is determined by the sequence of the gene.(4)
(Total for Question 10 = 12 marks)
The normal range of these cells in the blood is between 5×108 and 1.2×109 cells/dm3
An AIDS patient has a CD4+ T-Helper cell count of 1.5×108 cells/dm3
(a) Explain why the CD4+ count of 1.5×108 cells/dm3 has led to the diagnosis of AIDS. (2)
*(b) Some sexually transmitted infections (STIs) can be diagnosed by testing urine samples.
These tests use monoclonal antibodies that bind to an antigen on the pathogen.
Describe how a monoclonal antibody can be developed and used to detect an STI using a urine sample. (6)
(c) The antigens on pathogens can be proteins with a specific amino acid sequence.
Explain how the order of amino acids in a protein is determined by the sequence of the gene.(4)
(Total for Question 10 = 12 marks)