<span>Segregation would be the answer :)</span>
Humans get D vitamin from sunlight. the plants perform photosynthesis and grow , we eat those fruits and vegetables grown in the plants. so indirectly we humans and other animals are benifitted from sun sunlight . flesh eating animals eat herbivores animala so they are also benifitted
To much gas has build up in them? I guess
This would be probably true if the assumption that all possible genotypic variations would be equally distributed (so we would have 25% HH, 25% hh and 2x 25 Hh). If this distribution would be true and Huntingtons disease really was a single gene dominant trait diesase, then yes, we could expect such a distribution in the population.