A fish farm has repeatedly bred closely related salmon with a high harvest mass. A new disease kills most of these salmon.
Tests show that harvest mass and resistance to the disease are inherited characteristics.
The farmers cross females from the farm with males from three unrelated populations. The offspring are exposed to the disease and then reared under the same conditions. Offspring are counted as having both desired characteristics if they survive the disease and reach a harvest mass of at least 4.0 kg.
| cross | number of offspring tested | number of offspring with both desired characteristics |
|---|---|---|
| A | 160 | 64 |
| B | 200 | 138 |
| C | 120 | 54 |
Calculate the percentage of offspring from cross B that had both desired characteristics.
Explain which cross should be used to establish a population with both desired characteristics. Include how the farmers should continue the breeding programme.
100 exam-style questions on Edexcel GCSE Biology 4.3 Selective breeding and genetic modification, covering 4.3.1 Selective breeding and its impact, 4.3.2 Tissue culture, 4.3.3 Genetic engineering overview, 4.3.4 Main stages of genetic engineering, 4.3.5 Advantages and disadvantages of GM organisms, 4.3.6 Agricultural solutions for a growing population, and 4.3.7 Evaluating genetic engineering and breeding. Each one has a worked solution and a mark scheme showing where the marks go.