The results of the tests of three patients are given in the following table:
| | Positive Control | Negative Control | Patient R | Patient S | Patient T |
|-----------------|------------------|------------------|-----------|-----------|-----------|
| Optical Density | 1.689 | 0.153 | 0.155 | 0.675 | 1.999 |
Numbers are expressed as optical density at 450 nm - VCE - SSCE Biology - Question 25 - 2012 - Paper 1
Question 25
The results of the tests of three patients are given in the following table:
| | Positive Control | Negative Control | Patient R | Patient S | Patie... show full transcript
Worked Solution & Example Answer:The results of the tests of three patients are given in the following table:
| | Positive Control | Negative Control | Patient R | Patient S | Patient T |
|-----------------|------------------|------------------|-----------|-----------|-----------|
| Optical Density | 1.689 | 0.153 | 0.155 | 0.675 | 1.999 |
Numbers are expressed as optical density at 450 nm - VCE - SSCE Biology - Question 25 - 2012 - Paper 1
Step 1
A. patient R has not been exposed to HIV.
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Answer
Patient R's optical density is 0.155, which is much lower than the cut-off value of 0.500, indicating that patient R has not been exposed to HIV.
Step 2
B. patient R has been exposed to the HIV antigen.
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This statement is incorrect since patient R's optical density does not exceed the cut-off value, suggesting no exposure to the HIV antigen.
Step 3
C. patient S has responded to exposure to HIV by developing antibodies.
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Answer
Patient S's optical density is 0.675, which is above 0.500. This suggests that patient S has developed antibodies in response to exposure to HIV.
Step 4
D. the positive control contained fewer HIV antibodies than the negative control.
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This statement is false since the positive control (1.689) has a significantly higher optical density compared to the negative control (0.153), indicating it contains more antibodies.
