Many years ago, a scientist grew pea plants that
produced wrinkled peas. the peas from these
plants produced new plants that also produced
wrinkled peas. the scientist concluded that
something in the parent plants was being
transmitted to the next generation. this
discovery is now known as
(1) genetic engineering (3) heredity
(2) biological evolution (4) natural selection

The empty trna moves off and picks up another matching amino acid from the cytoplasm in the cell. the anticodon of the trna, with its attached amino acid, pairs to the codon of the mrna, which is attached to a ribosome. this sequence is repeated until the ribosome reaches a stop codon on the mrna, which signals the end of protein synthesis. the ribosome forms a peptide bond between the amino acids, and an amino acid chain begins to form. when a second trna with its specific amino acid pairs to the next codon in sequence, the attached amino acid breaks from the first trna and is bonded to the amino acid of the second trna.