In eukaryotic cells, the first stage of this process takes place in the nucleus and consists of specific portions of the DNA, called genes, being copied, or transcribed, into small strands of ribonucleic acid, or RNA. RNA containing a copy, or transcript, of DNA is called messenger RNA, or mRNA. These mRNA molecules are then physically transported out of the nucleus through the pores (holes) in the nuclear membrane and into the cytoplasm where they are eventually translated into proteins by ribosomes.