Lecture 31 & 32 Flashcards
which introns are autocatalytic
Group I and II
intron first hypothesis
Introns-first: In the “RNA world” introns could allow reshuffling functional RNA fragments by splicing them together
Intron early hypothesis
Introns-early: Introns in-frame allow for protein domains to be reshuffled in genes, prokaryotic introns lost over time once gene complexity established
Intron late hypothesis
Some introns continue to be lost or gained as species evolve and change
describe splicing fidelity
for genes with more than one intron, RNA may splice in different spots
What is one way to ensure splice sites aren’t skipped
initiating splicing during transcription
3 things
what can splicing control
Alter coding region, remove/include RNA regions which modify stability or how well it binds ribosomes affecting the rate of translation
Coding region, stability, translation rate
6 ways alternate splicing can generate protein variability
(A) Constitutive splicing
(B) Mutually exclusive exons
(C) Alternate exon / exon skipping
(D) Alternate 3′ splice site
(E) Alternate 5′ splice site
(F) Intron retention
What is the P element
transposable element that used to only be in fruit flies which was found to be in all wild flies today
WHat heppens if a P element is put into a human cell
always splices properly
What is the PSI? Where is it expressed?
P-element splice inhibitor
Binds the 5’ splice site at the end of exon 2 and blocks U1 binding
PSI is expressed in low levels in ovaries and testes so splicing is normal and transposase is made
What are the two P element proteins
66 kDa somatic protein that acts as a repressor blocking DNA from being cut and blocking the promoter
87 kDa germline protein is the transposase which binds the same sequence and cuts the DNA and inserts the element at a new location
They are self limiting
What happened when a wild female had p elements and they bred with a lab male? Inverse?
Wild female had p elements their whole life
so they had many repressor proteins that
was passed down to the offspring
when the father had the P element, there were no repressors in the egg and it was a defective baby
Is the P elements self-limiting? what happens when inserted into an uncolonized genome
Yes, they will rapidly insert until established enough to self-limit
Example of RNA interference
when a gene was added to petunias to make it more purple, it became white
RNA is interfering with the function of the normal RNA
