The poly-A tail is a long sequence of A nucleotides at the 3’ end of the transcript. When a sequence called a polyadenylation signal shows up in an RNA molecule during transcription, an enzyme chops the RNA in two at that site. Another enzyme adds about 100-200 adenine (A) nucleotides to the cut end, forming a poly-A tail. The 5’ cap and the poly-A tail help the mRNA transcript move to the ribosome from the nucleus. The tail makes the transcript more stable and helps it get exported from the nucleus to the cytosol.