Block 2 Lecture 6 from Gene to Protein Flashcards
what are the key principles of the central dogma
DNA is the heritable material, RNA is the messenger as proteins carry out cellular functions
what initiates transcription in eukaryotes
basal transcription factors
what is the role of a basal transcription factor
to match RNA polymerase to the appropriate promoter region of the DNA
where on the DNA is a TATA box
on the promoter commonly
which RNA polymerase in eukaryotes is responsible for the transcription of proteins
RNA polymerase II only
what does the transcription initiation complex consist of
transcription factors and RNA polymerase II
where do transcription factors bind to on a gene
the promoter, specifically the TATA box
What direction does RNA polymerase move in and in what direction is the new mRNA strand
RNA polymerase moves 3’ to 5’, the new strand is manufactures in a 5’ to 3’ direction
what speed does RNA polymerase unwind RNA during eukaryotic transcription elongation
10-20 base pairs at a time
on what end does the addition of new RNA nucleotides occur during transcription elongation
3’ end
what is the rate of transcription in eukaryotes
40 nucleotides per second
how is termination of eukaryotic transcription achieved?
RNA polymerase II transcribes a polyadenylation signal into the DNA
what is the polyadenylation signal at the end of an mRNA transcript
AAUAAA
what is a UTR
an untranslated region
what occurs immediately after eukaryotic transcription
eukaryotic mRNA processing
what does the 5’ cap consist of
modified guanine residue
what is the function of the 5’ cap
protect from degradation, aid stability and promote its export from the nucleus
what does the 3’ end of the mRNA contain
a poly-A tail
what does a poly-A tail consist of
50 to 250 adenine nucleotides
what is the function of a poly-A tail
stability
what part of the pre-mRNA is cut out
introns
what part of the pre-mRNA is spliced together
exons
what accomplishes splicing in a pre-mRNA transcript
a spliceosome
what are the key components of a spliceosome
several snRNP’s and proteins
what is an snRNP
snRNA and proteins
what does snRNP stand for
small nuclear ribonucleic protein
what specifically is the role of a spliceosome
CATALYSES the removal of introns and the joining of exons
what role does snRNA play in the splicing out of introns
snRNA sequence is complementary to the intron splice site
what affect does the number of A’s in a poly-A tail have on the rate of degradation of a transcript
more A’s slows down the rate of degradation
what is the name of the enzyme that charges tRNA by catalysing the addition of an amino acid to the tRNA
aminoacyl tRNA synthetase
does the addition of an amino acid to tRNA by aminoacyl tRNA synthetase require energy?
yes, one ATP is converted to AMP
what is an aminoacyl tRNA
tRNA covalently linked to its amino acid
is the binding site for an amino acid on a tRNA structure at the 3’ or the 5’ end?
3’
what shape does the tertiary structure of a tRNA molecule form?
L-shaped
what is the wobble hypothesis
the anticodon of tRNA can still bind successfully to a codon whose third base pair is non-standard
can one tRNA bind to more than one codon?
yes
where are ribosomes made and where do they operate
made in the nucleolus, operate in the cytosol or on the RER
what is the difference between a peptide and a protein?
peptide < 50 amino acids (oligopeptide)
protein > 50 amino acid
what part of the ribosome forms peptide bonds during translation
the large subunit
what is the function of the small ribosome in translation
hold the mRNA in place
what are the three locations of tRNA on a ribosome during translation
the A site, the P site and the E site
what is the A site on a ribosome
the acceptor site
what is the P site on a ribosome
the peptide bond site, where a peptide bond forms between the growing amino acids of a polypeptide
what are the three phases of translation
initiation, elongation and termination
what does the first aminoacyl tRNA, that binds to the small subunit of a ribosome, contain?
formyl methionine
what is the binding site during translation on an mRNA
the 5’ cap
The large ribosomal subunit ________ the formation of the a forming peptide bond on the growing polypeptide chain
catalyses
in which direction and to what site is the growing polypeptide chain transferred to during the elongation stage of translation
to the right, to the A site
what is the energy molecule present during elongation
GTP
how does termination take place during eukaryotic translation
release factor binds, water hydrolyses the bond between polypeptide chain and tRNA molecule, polypeptide released and 2 GTP used
