Sickle-cell trait is caused by a single defective allele, but sickle-cell disease only occurs in individuals that are homozygous for the sickle-cell allele. two people carry the trait but do not have sickle-cell disease. what is the probability that they will have two children with sickle-cell disease?

What kind of seafood would you expect to have the highest levels of mercury and why? kelp, because they use the sun to photosynthesize on the bottom trophic level. oysters, because they filter feed on plankton on a lower trophic level. small fish, because they eat plankton on a higher trophic level. sharks, because they feed on organisms on a higher trophic level.

During the winter, this species of fox has white fur, but in the summer, it has brown fur. what environmental change may have lead to this fox's fur color? snow cover increase in sun's brightness volcanic eruption global warming

In pea plants, yellow seed color (y) is dominant and green seed color (y) is recessive. based on the punnett squares, what are the chances that the offspring in the second generation will have green seeds?