Haemoglobin is the protein that carries oxygen in red blood cells. Scientists compared blood from people with one of two DNA variants, R or S, with blood from people with neither variant.
All measurements were made at the same oxygen concentration. The total oxygen carried by a blood sample depends on two things: how much haemoglobin it contains and how much oxygen each haemoglobin molecule carries.
Each value in the table is a percentage of the value for blood with neither variant.
| DNA variant | Haemoglobin quantity | Total oxygen carried |
|---|---|---|
| Neither variant | 100% | 100% |
| R | 100% | 40% |
| S | 60% | 60% |
Calculate the amount of oxygen carried per haemoglobin molecule with variant R, as a percentage of the value for blood with neither variant.
Explain which variant is more likely to be in coding DNA and which variant is more likely to be in non-coding DNA.
Blood is tested from a person who has both variants. Assume that each variant has the same effect when both are present as it has on its own.
Calculate the expected total oxygen carried, as a percentage of the value for blood with neither variant.
62 exam-style questions on AQA GCSE Biology 6.1 Reproduction, covering 6.1.1 Sexual and asexual reproduction, 6.1.2 Meiosis, 6.1.3 Advantages and disadvantages of sexual and asexual reproduction, 6.1.4 DNA and the genome, 6.1.5 DNA structure, 6.1.6 Genetic inheritance, 6.1.7 Inherited disorders, and 6.1.8 Sex determination. Each one has a worked solution and a mark scheme showing where the marks go.