Which primers in RT-PCR are specifically designed to amplify mRNA with polyA tails?

The correct answer is Oligo dT primers because they are specifically designed to bind to the polyA tails found at the 3' end of mRNA molecules. This property allows Oligo dT primers to selectively amplify mRNA from a mixture of nucleic acids, such as total RNA, because they will hybridize exclusively to mature mRNA that contains these polyA tails.

When performing reverse transcription, the synthesis of complementary DNA (cDNA) from mRNA relies on the binding of these Oligo dT primers, ensuring that only mRNA is converted into cDNA. This selective amplification is critical for applications where the goal is to analyze gene expression or produce cDNA libraries from specific mRNAs.

In contrast, random hexamers bind non-specifically to various RNA sequences, meaning they can initiate cDNA synthesis from any type of RNA, not just mRNA with polyA tails. Target-specific primers are designed to amplify specific sequences and are generally used in subsequent PCR cycles after cDNA synthesis, rather than in the initial reverse transcription step. Non-specific primers can bind to any RNA, leading to unwanted amplification and potential contamination in the results. Therefore, the specificity of Oligo dT primers for polyA-ta