Basic Principles of Transcription and Translation - Computer ...

5′
Protein
snRNA
RNA transcript (pre-mRNA)
Exon 1 Intron Exon 2
5′
snRNPs
Spliceosome
components
5′
Spliceosome
mRNA
Exon 1 Exon 2
Other
proteins
Cut-out
intron
The roles of snRNPS and
spliceosomes in pre mRNA
splicing. The diagram shows only
a portion of the pre mRNA
transcript, additional introns and
exons lie downstream from the
pictured ones here. 1) Small
nuclear ribonucleoprotein
(snRNPs) and other proteins form
a molecular complex called a
spliceosome on a pre mRNA
molecules containing exons and
introns. 2) Within the spliceosome
snRNA base pairs with nucleotides
at specific sites along the intron. 3)
The spliceosome cuts the pre
mRNA releasing the intron and at
the same time splices the exons
together. The spliceosome then
comes apart releasing mRNA
which now contains only exons.
Ribozymes
Ribozymes are catalytic RNA molecules that function as
enzymes and can splice RNA
The discovery of ribozymes rendered obsolete the belief
that all biological catalysts were proteins
Three properties of RNA enable it to function as an
enzyme
It can form a three-dimensional structure because of its ability to
base pair with itself
Some bases in RNA contain functional groups
RNA may hydrogen-bond with other nucleic acid molecules