Final answer:
Single gene mutations like those causing sickle cell anemia and cystic fibrosis can affect multiple traits because the same gene can influence different physiological processes, leading to both disease and resistance to infections like malaria and cholera, respectively.
Step-by-step explanation:
More than a single trait is affected by mutations like sickle cell anemia and cystic fibrosis because these conditions are the result of mutations in single genes that can have multiple effects on the organism's physiology. In the case of sickle cell anemia, the mutation causing the disease also provides a resistance to malaria. This is due to the altered shape of red blood cells, which makes it more difficult for the malaria parasite to infect and replicate within them. Carriers of the trait, with just one mutated gene, have some resistance to malaria without exhibiting full-blown sickle cell anemia. Similarly, carriers of the cystic fibrosis gene mutation are resistant to cholera because the defective chloride channels in their cells make it difficult for the cholera toxin to exert its effects. Both of these mutations are examples of how a single gene can influence more than one trait, and they demonstrate the complex relationship between genetics, disease resistance, and evolutionary survival in different environments.