Unit 3A Transcription DNA -> RNA Flashcards
What is central dogma
dna to rna (genotype) to protein (effect or activity of protein) (phenotype)
nucleotide structure
ribose (OH - RNA vs H - DNA)
C 3 is the phosphate linkage
C5 is going to have the phospherdiester bond
which direction can nucleic acids grown in
which strand are we not using
5’ - 3’ direction
non template strand
Why is non template strand called coding strand
generate rna through transcribing the template compare to coding strand, they will be identical except Uracil will be swaped in with Thymine
What is RNA polymerase (RNApol)
transcription mediator
unravels DNA
reading strand 3 - 5 direction but building DNA on to 3’ end
many rna polymerases will be transcribing gene at same time
not all RNA’s code for proteins
large, globular enzyme with several channels running through it
active site is at intersection of channels
Holoensyme made up of core enzye which has ability to synthesize RNA and regulatory subunit (sigma factor)
RNApol details
holoenzyme - core enzyme and sigma foactor (subunit)
core enzyme polymerizing to create enzyme based on the template
sigma recognizes where the gene starts (recognizes of promoter that has to be upstream of the start of the gene)
core RNApol + sigma factor —> RNA polymerase holoenzyme
sigma factor
working upstream (-10 is ten bases up from gene)
using 2 characteristic sequences (-10 and -35 boxes) helps to start coding at right spot
they are on coding (non template strand)
how to stop reading transcription
aka finish transcription
somewhere in sequence hit a sequence that causes complementary bases to come out that cause hairpin sturcture to form
forms spontaneously
destabilizes complex and falls apart
how many RNA polymerates do eukaryotes have
3
RNApol I, II, III
RNApol II focus on
General Transcriction Factors
TATA box recognized by TBP (tata binding protein subunit of trans factor II D) leads to alignment
TFIIH pries apart double helix at transcription start point
What happens to mRNA before it leaves the nucleus
a lot of processing happens before it goes out of nucleus for translation
Phosphorelated tails
a lot of modifications associates with PT
capping factors, splicing factors, polyadenylation factors
changes can happen as transcription is going on
mRNA Capping
involves 7-methulguanosine
coding part,
poly-A tail protects from degradation extends half life
what is splicing
seperating coding stretches of the transcript from the non coding sequences
separeting exons from introns
coding regions are
noncoding regions are
exons (express, directing sequence)
introns (pulling out introns)
what does pre-mRNA contain
entire gene (introns +extrons)
what do introns contain
after capping, while still being transcribed, RNA splicing (removal of introns) begins. Each intron contains few short sequences at/near its ends that are cue for its removal
how does intron removal work
intron has signals at both sides
molecular machenery cut backbone, form circle
exons bond together
end up with circular intron that degrades
what molecular machinery allows removal of introns
spliceosomes
has 5 small nuclear ribonucleaic particles (snRNPs)
RNA + 100 + proteins
catalutic activity provided by RNA component
what are advantages of RNA splicing
can create different proteins from same gene/same primary RNA
exon skipping
disadvantages of RNA splicing
more steps - more work
higher probability for mistake
makes transcription more complicated
What needs to happen for mRNA to leave nucleus
5’ cap and poly-A tail are marked by protiens
exon junction complex (group of proteins) binds to properly spliced mRNAs
