Which of the following is true about the nucleus? a. it is surrounded by a single phospholipid membrane b. it is where glycolysis occurs c. it is the site of protein synthesis d. it contains the cell’s dna and rna

Which of the following is not a main characteristic that scientists focus on when determining which kingdom an organism belongs to

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.

Which best describes how the common cold spreads in the human body? a bacteria burst out of normal cells killing them b viruses replicate inside respiratory cells c bacteria inject dna into normal cells d viruses insert dna into bacteria