Page 236 - The Manga Guide to Biochemistry

mRNA

The enzyme called RNA polymerase enables genes that are written in the
DNA—that is, their base sequences—to be used as templates to synthesize
RNA with complementary base sequences.

This process is called transcription (it can also be referred to as RNA
synthesis), and the synthesized RNA is called messenger RNA (mRNA).

For example, take a look at the gene shown in the following figure.

Sense strand

5´ 5´
3´ RNA synthesis direction

3´ 3´

mRNA

5´

AntiSense strand

Gene

DNA is double stranded, and, for each gene, only one side of the DNA is mean-
ingful (that is, its base sequence becomes the blueprint). This is the sense strand
for that gene. The other strand, which is complementary to the sense strand, is
called the antisense strand.

That makes...sense.

Since mRNA is synthesized using the antisense strand as a template, the base
sequence of the RNA that’s produced is the same as that of the sense strand.
However, where the base is T (thymine) in the sense strand, there will be a U
(uracil) in the mRNA.

222 Chapter 5