Human mutations may increase resistance to some infectious diseases. Humans which carry the mutant gene, the "sickle cell allele" , may be more resistant to death caused by - and humans which carry the cystic fibrosis allele may be more resistant to death caused by

correct answer is a. and d.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

if you add everything up correctly you should get 69 i got this because 50 plus 19 is it