Coupon Accepted Successfully!


The Synthesis of RNA

The synthesis of RNA is similar to DNA replication (see Chapter 5). The template DNA strand is denatured and an RNA copy complementary to the template is synthesized. The same base pairing rules apply (except that U substitutes for T in the RNA molecule). Transcription is similar to replication in that it must proceed (the RNA must be built) in the 5’ to 3’ direction.

Three major differences distinguish transcription from replication:
  • Only one stretch of DNA (the gene) is copied in transcription, unlike the entire DNA molecule in replication. Also, only one strand of the DNA is copied, not both;
  • The resulting copy of RNA is single stranded, not double stranded as in replication;
  • The enzyme responsible for making RNA is called RNA polymerase. 
The transcription of mRNA begins when RNA polymerase binds to a specific sequence of nucleotides just in front of the gene, called the promoter. The enzyme then begins making an RNA copy of the DNA template, and continues until it reaches a stop sequence at the end of the gene. The RNA polymerase then releases the transcript (see Figure 6.2).
At this point, the RNA is technically known as pre-mRNA. All transcripts go through further processing before being translated. 

Test Your Skills Now!
Take a Quiz now
Reviewer Name