Alternative RNA Splicing


Many genes in our body are expressed as RNA in different cell
types, a skin cell, a bone cell, a brain cell. But in one cell type, the pattern of splicing of the sense
pieces together is different than the pattern in
another cell type and that’s called alternative splicing. So its alternative splicing because the
splicing pattern in one cell is different then the splicing pattern in another cell and therefore the proteins in those two
cells are different. And that can make a great deal of difference because
one protein can function, splicing one pattern in one cell one way and then another spliced differently in another way. So, you know, if you’re designing drugs or
you’re looking at functionality of mutations they can differ due to this alternative
splicing between different cells. Alternative splicing means that the splicing machinery selects certain exons or parts of certain exons differently in a proportion of
the molecules that it splices. So it’s a way to take a gene and, from
its primary transcript, generate two or more RNAs that can encode two
or more proteins. The splicing machinery has a choice. It sees this
string of exons and it chooses what to join to what. It isn’t always product A or product B, you could have
some proportion of the molecules choose pathway A and the rest choose pathway B and that is the case with SMN2. If it
were to completely skipped exon 7, that may be a lethal change in the
absence of SMN1. In reality, it makes some full-length
protein.

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