Class Notes (808,703)
Canada (493,376)
Biochemistry (847)
Eric Ball (118)

Biochem Brandl 4

4 Pages
Unlock Document

Western University
Biochemistry 2280A
Eric Ball

Biochem - Lecture 4 - Nov. 15th Formation of mRNAs - RNA Processing (Eucaryotes): • primary transcript becomes a mRNA for export out of the nucleus and translation • 5’ capping • 3’ polyadenylation • splicing RNA Processing: • 5’ capping, 3’ polyadenylation and splicing are concerted processes (that is they happen together) • 5’ capping, 3’ polyadenylation and splicing - each requires a specific enzyme or enzymes 5’ Capping: • Figure 7.16 • 7-methylguanosine is added to 5’ end of the RNA Importance of the 5’ Cap: • marks the 5’ end of the mRMA as being intact • required for mRNA export from the nucleus • required for translation of the mRNA into protein (translational initiation) 3’ Polyadenylation: • sequence AAUAAA is recognized by enzyme that cleaves just after that se- quence; another enzyme comes in and adds long PolyA tail • PolyA tail helps protect the 3’ end of the mRNA from degradation • indicates that the 3’ end of the mRNA is intact and therefore is important for ex- port out of the nucleus and for translation Splicing: • Figure 7.17 • in eucaryotic cells protein encoding sequences are interrupted by one or more noncoding sequences called introns (genes are interrupted) • exons: expressed, introns; interruptions • introns are spliced out of the primary transcript to give the mature mRNA • Figure 7.18 (human beta-globin gene) • genes differ in their intron/exon complexity Why is Splicing Important? • Differential Splicing: • a single RNA can be spliced in different ways to create related but dis- tinct proteins • splicing enhances the coding capacity of the genome • Question: Assuming the 5’ most exon is always expressed and splicing occurs in a linear fashion (5’-3’), how many gene products could be made from the following gene? 5’ -------Exon 1------Exon 2-----------------Exon 3-----------3’ • 4 gene products • Exon 1 expressed alone (no introns are spliced out) • Exon 1 and 2 (intron A is spliced out) • Exon 1 and 3 (splice exon 1 and exon 3 together, removing Intron A-Exon 2-Intron B) • Exons 1, 2 and 3 (Intron A and Intron B are spliced out) • splicing adds to the complexity of the genome • Tissue Specific Differential Splicing: • Figure 7.21: tropo
More Less

Related notes for Biochemistry 2280A

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.