A2 functional diversity through mRNA splicing Flashcards
how many introns does the average human gene have and what size are they
8 but some have >100
from 50 to 10,000 nts
what does the cap on pre-mRNA involve
involves methylation of bases
and formation of rare 5’ to 5’ triphosphate bridge with GTP
occurs when pre-mRNA is around 25 nt long
involves specific capping proteins
enhances stability and is key for efficient translation
what does the Poly(A) tail on pre-mRNA involve
Poly A added by enzyme called poly(A) polymerase
(A)n where n may be 250+
increases stability and enhances translation
what do all introns start and end with
start with GU and with AG
what is the key to splicing introns
a pyrimidine rich tract (PY)n and a specific adenine
splicing proteins recognise specific sites, what are these
the GU at the 5’ splice site and the branch site
the proteins involved in splicing recruit other proteins into the large complex called what
spliceosome
what can the spliceosome do
can capture, splice, and release RNA accurately and in a coordinated way which involves a careful choreography of spliceosome components
what is alternative splicing
a process whereby different mRNAs are generated from the same initial (primary) transcript
what can cause disease by affecting splicing
mutations
what can happen when splicing goes awry
formation of a non functional protein or mutated one
how can some RNA mols self splice
because RNA can fold into distinct structures it has the capacity to act as an enzyme and splice itself
what drives splicing within the RNA structure
short stretches of nts on RNA can bp with other regions creating folds which in turn drives splicing
who discovered that RNA can act as an enzyme and self splice
tom cech and sidney altman
what is RNA interference
RNAi is a powerful tool to disrupt gene expression
discovered when double stranded RNA was introduced into a cell
found to suppress the transcription of genes that contained sequences present in the original double stranded RNA
what does RNAi reply on
key activity of small interfering RNAs (or siRNAs)
what is RNAi widely used in SIPBS for
to silence the expression of specific genes
why is RNAi exploited in cell biology
to examine the function of a particular gene product by silencing other genes
what is the name given to genome editing
CRISPR/Cas
technology behind CRISPR/CAs
specific guide gRNA is synthesised that directs an endonuclease enzyme called Cas( to specific DNA target sequence
can be used to create a cleavage in the DNA at a precise point and so insert or delete nucleotides (or create a frameshift)
what are the potential uses or CRISPR
-poweful lab tool to create cell lines to probe specific gene function by creating a ‘knockout’
-can produce specific mutations in the germ line- probe function of key putative residues in a protein
-can be used ex vivo and in vivo genome editing for clinical therapy
ex vivo genome editing for clinical therapy
cells isolated from a patient to be treated
edited then regrafted back to patient
to achieve therapeutic success, the target cells must be able to survive in vitro ad=nd return to the target tissue after transplantation
in vivo genome editing for clinical therapy
engineered nucleases are delivered by viral or nonviral approached and directly injected into the patient for systemic or targeted tissues (ie eye, brain, or muscle) effect
