transcription Flashcards
reverse transcriptase
RNA-dependent DNA polymerase. enzyme that generates complementary DNA from an RNA template, It is mainly associated with retroviruses. (HIV)
RNA polymerase:
DNA dependent RNA polymerase. uses a DNA template to make RNA
DNA polymerase
DNA dependent polymerase. needs a DNA template to make DNA
central dogma
DNA->RNA->proteins
T/f: RNA polymerase has editing function
false
which type of rna is involved in coding genes
mRNA
do mitochondria and chloroplasts have the same set of RNA polymerases as regular cells?
no. they have their own.
- Not coded for in nucleus.
- Makes sense in light of endosymbiotic theory.
describe prokaryotic RNA polymerase?
- have only a single type of RNA polymerase. Closely related to one found in mito, chloroplasts.
what tells RNA polymerase where to begin transcription?
promoter sequence
what tells RNA polymerase to stop making RNA?
termination signal
small factor in bacteria called ___that helps RNA polymerase recognize promoter sequence that it needs to get starteds and run ‘de novo’ after starting
sigma factor
what’s interesting about the 5’ end of the newly synthesized strand of RNA?
5’ end of this RNA has 3 phosphates on it- as no nucleotide is attached to it
in what kind of organism would you find a ta ta box?
prokaryotes
what would you find in the promoter region of prokarytoes?
- -10 sequence ( ‘ta-ta box’)
- -35 sequence. (not all have this, but most do.) These are called consensus sequences.
consensus sequences
10’, 35’ sequences at promoter region of prokaryotic DNA
Promotor region
- a sequence of DNA that tells the RNA polymerase where to sit down to begin transcription
Rho protein termination
Rho protein jumps on if it sees a rho sequence, twists itself, breaks it away from polymerase to end transcription. ‘rho dependent termination
. Hairpin/Rho independent termination- what is it and where does it occur?
prokaryotes- stops transcription. sees some sort of complementary regions, folds so those regions pair. That causes the transcription to stop
what does it mean when we say direction of transcription is determined by orientation of promoter
Transcription is asymmetric, i.e. each gene is transcribed in only one direction such that if the lower strand serves as the template (e.g. gene C), then the upper strand will not be a template for other transcription . it goes in whatever way the promoter sequence is facing.
polycistronic transcripts and where you would find them
coding for more than one gene in a single transcript . prokaryotes.
looking at this photo- where is the promoter region?
far left of each blob.
shortest = at start. Longer strands = happening later. Little black dots are rna polymerase
pro or euk mRNA: has a methyl guanine added on to 5’ end . ‘5’ cap’ added on in order to protect the RNA from the enzymes so they can’t chew it up
eukaryotic
what do we mean when we say Eukaryotic mRNA has modifications at ends
5’ cap and tons of A’s (adenylation) at 3’ end
how many genes do eukaryotic mRNA transcripts contain information for
just one
Exons and introns
Exons are expressed sections. Introns are sections of noncoding regions- not expressed.
do bacteria have exons/introns?
no
examples of introns and exons in real genes
- Beta globin: 3 exons 2 introns.
VIII gene: clotting factor for hemophilia: 26 exons, 25 introns
mature mRNA
mRNA with all introns removed- ‘ready to go’
what are the 2 modifications eukaryotes make to mRNA
capping , adenylation
Rna splicing
specifically removes introns from RNA. (happens in nucleus) to produce the mature mRNA
snRNP’s
SNRPS perform RNA splicing
splicers gon splice.
how do SNRP’s splice?
- Form base pairs with 5’ end of intron and 3’d end of intron
- Always an A nucleotide in there
- Pull the 2 sections together. Bend it around and attach it to the A. ‘lariat’ like a lasso rope appearance. Cut off 3’ end of intron, hook ends of exons together. Throw away the intron lasso thing. Happening at every intron/exon junction.
How can we do everything we do with only 23,000 genes?
alternative splicing
___can generate multiple proteins from transcripts from a single gene
Alternative splicing
where is prokaryotic RNA translated
out in the cytoplasm- no nucleus!
describe the process that has to occur before eukaryotic mRNA can be translated
- nuleus surrounding all DNA: Transcribe in nucleus. Then cap. Then polyadenalate. Then splice out introns. All that to get a mature mRNA. Then ship to cytoplasm. Then and only then translation begins.
Translation:
process of using sequence in mRNA to code for a protein.
transfer rna’s
little short rna’s 100 nucleotides long that have job of bringing amino acids to the site of translation, where proteins are being made
anticodon region of tRNA
a sequence of three bases in tranfer RNA that are complementary to a codon in the messenger RNA
___end of tRNA is where amino acid attaches
3’
tRNA synthetase
charges tRNA’s aka Puts amino acids onto them
tRNA synthase enzyme takes an amino acid and hooks ___ terminus onto ___end of tRNA. gets the energy from:
COOH , 3’
- Uses an ATP to generate a high energy bond. Here we convert ATP to AMP- break off TWO phosphate.
