What prevents the total elimination of variation in a population when one variety is obviously more competitive in each environment? **use your knowledge of recessive and dominant alleles to help you**

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Genetic disorders can result when sister chromatids fail to seperate properly. during what phase is this problem most likely to occur?

When fossil fuels are burned, carbon dioxide is released. how does this gas impact the environment?