A chemical similar to a single strand of DNA. In RNA, the letter U, which stands for uracil, is substituted for T in the genetic code. RNA delivers DNA's genetic message to the cytoplasm of a cell where proteins are made.

Dr. Leslie Biesecker, of the National Human Genome Research Institute's Laboratory of Genetic Disease Research, defines RNA.

Related terms: cell, deoxyribonucleic acid (DNA), genetic code (ATGC), messenger RNA (mRNA), protein.