AP BIOLOGY

Detailed explanation-1: -As a first step, isolated mRNA is converted to a complementary DNA (cDNA) molecule with an RNA-dependent DNA polymerase, also known as reverse transcriptase, during a process called reverse transcription. The cDNA can be used as any other DNA molecule for PCR amplification.

Detailed explanation-2: -Reverse transcriptase is used to make a cDNA copy of the mRNA. The cDNA sample is then amplified by PCR. This yields multiple copies of cDNA without introns. Reverse transcription followed by PCR allows cloning of genes starting from the messenger RNA, and thus, identifying the expressed exons of the eukaryotic gene.

Detailed explanation-3: -Enzymatic conversion of mRNA into double-stranded insert DNA can be accomplished by a number of different procedures. All of them involve the action of reverse transcriptase and oligonucleotide-primed synthesis of cDNA. After that, the procedures in common use diverge considerably.

Detailed explanation-4: -cDNA is a more convenient way to work with the coding sequence than mRNA because RNA is very easily degraded by omnipresent RNases. This the main reason cDNA is sequenced rather than mRNA. Likewise, investigators conducting DNA microarrays often convert the mRNA into cDNA in order to produce their probes.