Mitochondria and chloroplasts are thought to have originated as prokaryotic endosymbionts, true or false?

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.

How does an angiosperm prevent self pollination

Aparent with freckles is crossed with a parent without freckles. the punnett square shows the possible genotypes and phenotypes of the offspring. which statement accurately describes the probability of phenotypes? a. the offspring are more likely to have freckles. b. the offspring are more likely to have no freckles. c. the likelihood of the offspring having freckles and not having freckles is the same. d. the likelihood of the offspring having freckles and not having freckles cannot be determined.