Smallpox viruses can replicate only inside a human cell. Human influenza viruses can replicate in human cells and in the cells of pigs and some other animals. How might this difference influence the success of vaccination programs?

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

answer increasing the intensity, duration,and frequency of exercise progressively;

while the heads of the phospholipid structure attract water, the tails are hydrophobic. the model shows how the hydrophilic section folds around the fluid molecules to bring them into the cell so they don’t need to pass through the hydrophobic tails.