Which best explains the importance of a selectively permeable cell membrane? a it prevents bacteria and viruses from entering the cell. b it controls which proteins are synthesized in the cell. c it controls what is allowed to enter or leave the cell. d it prevents the loss of too much water from the cell.

Choose the best definition of allele. a. one of several possible versions of a gene, which each produce a different phenotype b. an organism that's purebred for a given trait c. the process of fertilizing a plant with pollen from another plant d. a set of genes that are located on the same chromosome and so are tightly linked