A breeder started with a population of farmed trout with a mean body mass at harvest of 0.86 kg.
Two selective-breeding programmes were used for ten generations. Fish in both programmes were reared under the same conditions. After generation 10, the same new disease spread through both populations.
| Breeding programme | Selection of parents in each generation | Mean body mass at harvest in generation 10 (kg) | Offspring with an inherited disorder (%) | Fish that survived the new disease (%) |
|---|---|---|---|---|
| X | The offspring with the largest body mass from the same family line were bred together | 1.31 | 12 | 24 |
| Y | The offspring with the largest body mass from several unrelated family lines were bred together | 1.29 | 4 | 63 |
Explain why both breeding programmes increased the mean body mass of the trout.
Explain why programme X produced a higher percentage of offspring with an inherited disorder and a lower percentage of fish that survived the new disease than programme Y.
The breeder wants to maintain a high mean body mass while reducing inherited disorders and losses from disease.
Suggest which breeding programme should be continued. Use the information in the table to support your answer.
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.