lecture 25 Flashcards
what is gRNA
Some RNA editing is carried out by
guide RNAs (gRNAs) that can be made
in the cell.
How does gRNA inset uridine inside the mRNA
gRNAs direct the insertion of uridine
bases into the mRNA by a repair
polymerase
how does gRNA modify the mRNA
gRNA modifies the mRNA by
making new codons that specify new
amino acids in the protein.
what are apolipoproteins
Apolipoproteins are blood proteins that carry lipids (fat
and cholesterol) in the blood stream
what is the process of Editing of Apoplipoprotein-B mRNA
RNA editing of ApoB by an
enzyme called, cytidine deaminase
changes “C” to “U” converting a normal
glutamine codon (CAA) to a
termination codon (UAA), which
truncates the protein and gives it
a different function with respect to
lipid binding.
5. RNA molecules and RNA processing (cont’d)
The anticodon of the tRNA base
pairs with the codon of……….
The anticodon of the tRNA base
pairs with the codon of mRNA.
What is ribosome
A ribosome is an “RNA machine” with key roles in protein
synthesis, including the formation of peptide bonds
between amino acids
where is the site of ribosome synthesis in the eukaryotics
The nucleolus: site
of eukaryotic rRNA
synthesis and
ribosome assembly
whare does ribosome synthesis happen in the prokaryotics
Of course, in prokaryotes
there is NO nucleus and so,
rRNA synthesis and ribosome
assembly occurs in the
cytoplasm.
what does snRNA do
-snRNAs act in complexes with proteins.
-play roles in post-transcriptional processing of RNA, such as
splicing (spliceosome assembly)
snoRNA do?
snoRNA- also act in complexes with proteins.
-in eukaryotes, guide the enzymatic chemical modifications of
ribosomal RNAs, transfer RNAs and small nuclear RNAs
Eukaryotes do ?
act as short (~22 nt), single-stranded RNAs that bind to complementary sequences in mRNA.
-produced by cleavage of mRNAs, RNA transposons, and RNA viruses.
-regulate and control gene expression in different ways
what isLong noncoding RNAs ?
-known to function in eukaryotic cells. Longer than micro-RNAs (200-100,000 nt long).
-Significant: about 80% of the mammalian genome consist of non-protein
coding RNAs!
function of the noncoding RNAs
regulate and control gene expression at the level of transcription or
translation by binding mRNA or sequestering micro-RNAs that control gene
expression.
OR
-bind and recruit proteins involved in DNA modification (i.e., Xist RNA
controls the binding of proteins that methylate DNA sequences contributing
to X chromosome inactivation in mammals).
