3' end

3' end refers to the end of a nucleic acid molecule, the opposite of the 5' end. The 3' end is the end of the molecule that has a free hydroxyl group attached to the 3' carbon of the ribose (or deoxyribose in the case of DNA).

Structure and Function

The 3' end of a nucleic acid molecule is important in both DNA replication and transcription. During DNA replication, new nucleotides are added to the 3' end of the growing DNA strand. This is because DNA polymerase can only add nucleotides in the 5' to 3' direction.

In transcription, the 3' end of the mRNA molecule is where the poly-A tail is added. This tail is important for the stability of the mRNA molecule and aids in its export from the nucleus to the cytoplasm.

3' End in DNA Replication

During DNA replication, the 3' end of the new DNA strand is where the DNA polymerase adds new nucleotides. The DNA polymerase moves along the template strand in the 3' to 5' direction, adding nucleotides to the 3' end of the new strand. This results in the new DNA strand growing in the 5' to 3' direction.

3' End in Transcription

In transcription, the 3' end of the mRNA molecule is where the poly-A tail is added. This tail, composed of a string of adenine nucleotides, protects the mRNA molecule from degradation, aids in its export from the nucleus to the cytoplasm, and plays a role in translation.

See Also

• 5' end
• DNA replication
• Transcription
• Translation