Alternative RNA Splicing

A DNA segment can code for different forms of
mRNA when different introns are removed from
the primary transcript (alternative splicing). By
means of alternative gene splicing, a gene can
code for different, albeit similar gene products.
This allows a high degree of functional flexibility.
Numerous examples of differential RNA
splicing are known for mammalian genes. For
example, the primary transcript for the calcitonin
gene contains six exons. They are spliced
into two different types of mature mRNA. One,
consisting of exons 1–4 (but not exons 5 and 6),
is produced in the thyroid and codes for calcitonin.
The other consists of exons 1, 2, 3, 5, and
6, but not exon 4. It codes for a calcitonin-like
protein in the hypothalamus (calcitonin generelated
product, CGRP).