Which activity is accomplished using the genetic code?

mRNA molecules are transcribed to form tRNA

Cells make proteins

RNA molecules are copied before mitosis begins

Polypeptides are made into mRNA

(A) Cells make proteins

Proteins are composed of amino acids. Proteins are made in a process called translation, in which the cell commands.

(B) RNA molecules copied before mitosis begins

DNA molecules are copied before mitosis, not RNA.

(C) mRNA molecules are transcribed to form tRNA

DNA is used as template to form both mRNA and tRNA in a process called transcription.

(D) polypeptides are made into mRNA

mRNA is the template used to make polypeptides in a process called translation.

Therefore, A is the right answer.