a. To make a copy of DNA from mRNA one would use an mRNA template, a poly(dT) primer (underlined sequence in 1b), DNA nucleotides, retroviral reverse transcriptase enzyme, and the proper buffer and incubation conditions. This process is also known as reverse transcription.
b. mRNA sequence 5’ GAATCGGCTAGACAAAAAAA 3’
cDNA sequence 3’ CTTAGCCGATCTGTTTTTTTT 5’
c. Since mRNA in eukaryotes contain a 3’ polyA tail but tRNA, rRNA, and other RNA do not, one can use a poly(dT) primer to selectively create a cDNA library that only contains the spliced (no introns), protein-encoding regions of the genome.