Poly-dT refers to a polymer of deoxythymidine, which is a nucleic acid sequence composed of repeated thymidine (T) residues. It is often used in molecular Biology applications, such as in the synthesis of cDNA from mRNA, where it serves as a primer for reverse transcription, especially for mRNAs with poly-A tails. Poly-dT can also be used in various assays and experiments involving DNA or RNA manipulation and analysis.