friday week 2 Flashcards
transcription
DNA to RNA
translation
RNA to protiens
gene expression
the flow of information in a cell from a DNA encoded gene to a functional protein or RNA product
classes of RNA
- messenger RNA
- rhibosomal RNA
- transfer RNA
mRNA
messenger RNA.
mRNA is translated into protein
rRNA
ribosomal RNA
an essential part of the ribosome. where protein synthesis occurs (mixture of RNA + proteins, RNA does the work protien for structure)
tRNA
transfer RNA
intermediary molecule in the translaton of mRNA to protein
operon
a group of genes transcribed together to form one large protien
polycistronic
mRNA moolecule from operon transcription (multiple rhibosomes producing on one DNA strand)
promoter
sequence where RNA polymerase (and general transcription factors) binds to start/innitiate transcription
operator
sequence bound by regulatory protein that modifies gene expression levels
terminator
sequence of DNA at which RNA polymerase stops transcribing
general transcription factors (GTFs)
GTFs (along with RNA polymerase) binds promotors to initiate transcription
transcription factors (DNA binding proteins)
transcription factors regulate gene expression by binding to enhancer and silencer sequences to activate or repress transcription.
determins when/where/how much transcription occurs for a specific gene
5’ UTR
region of mRNA upstream of the start codon that is not translated (still transcribed)
3’ UTR
region of mRNA downstream of the start codon that is not translated (still transcribed)
exons
section of transcribed mRNA that can be translated. encode amino acid sequences
introns
section of transcribed mRNA that act as intervening non-coding sequences. get spliced out of mRNA strands and are thus not translated
which direction does translation go
5’ to 3’
do you use the top or bottom strand to do transcription
either! you just go a different direction when you use top/bottom strand
coding strand
strand that matches the mRNA strand
template strand
strand that complements the mRNA strand
RNA polymerase
enzymatic protein complex that unzips the DNA for transcription.
doesnt need helicase or primer
how does RNA polymerase get its energy
phosphoanhydride bond from NTP (nucleotriphosphate, aka incoming nucleotide)
where does RNA go after its built
RNA is not attached to the template DNA and eventually leaves nucleous to go to cytoplasm as mRNA
steps of bacterial transcription
- RNA polymerase innitiates transcription at the promoter (binds at promoter)
- RNA polymerase moves along template strand in a 3’ to 5’ direction SYNTHESIZING complementary RNA strand in a 5’ to 3’ direction
- transcription stops and RNA polymerase ‘falls off’ at the terminator sequence
general transcription factor (eukaryotic transcription)
TF2D subunit, TATA binding protien (TBP) binds to tata box in the promoter
how transcription process starts
general transcription factors + RNA polymerase 2 are recruited to the promoter to form the transcription initiation complex:
-TF2D phosphorylates the tail of RNA polymerase II to initiate transcription
- TATA binding proteins bind to DNA which signals everything else to come in and start transcription (building transcription initiation complex)
three steps of RNA transcription
- RNA processing converts a pre-mRNA to a mature mRNA
- pre-mRNAs are capped, spliced, and polyadenylated
- mature mRNA is exported from nucleous
mRNA capping
the 5’ end of an mRNA is capped with a 7-Meg modified nucleotide with unusual 5’ to 5’ linkage
what is the purpoes of mRNA capping
adds stability to RNA molecule. is required for mRNA export from the nucleous + is important in translation
mRNA polyadenylation
mRNA is cleaned and poly-A polymerase (PAP) adds A’s to the 3’ OH end of the RNA molecule
what is the purpoes of mRNA polyadenylation
poly-A tail protects mRNA from degradation and influences translation
mRNA splicing
process of removing the introns so they are not translated into protein(s)
what is the slicesome made of
composed of snRNPs (small nuclear RNAs and proteins)
snRNAs of the splicesome are rhibosomes, RNA acts as the catalyst
process that occurs in slicesome (go through steps)
- splicesome catalizes formation of a lariet structure
- the 5’ and 3’ splice sites are cleaved and the two exon ends are joined
- intron is degraded
what happens post capping, polyadenation, splicing…
- mRNA is complete in the nucleous + protiens bind to it to signal sites
- mRNA exits the nucleous through nuclear poors
- proteins on mRNA swap with proteins that innitiate protein synthesis
- TRANSLATION OCCURS
genetic code
the way in which a sequence of 20+ things is determined by a sequence of four things of a different type. the basis for how genetics work.
genetic code is nearly universal accross all species
codon
section of 3 bases. sequences of 3 bases (codons) are the basic units of the genetic code.
what does a codon do
codes for a single amino acid or a ‘‘stop”
how many codons code for an amino acid
depends! some amino acids have 5+ codons that code for them, others have only one
what does it mean that the genetic code is redundent/degenerative
multiple codons can code for one amino acid
reading frames
where one starts to ‘read’ the mRNA sequence. 3 reading frames on each mRNA molecule. the different frames are the first three letters present in the sequence. when you start at different reading frames, you get different codons which code for different amino acids
transfer RNA (tRNA)
adaptor between the mRNA codon and the amino acid
anticodon
tRNA version of mRNA codon which then covalently bind w/amino acid (tRNA anticodons build 5’ to 3’ which is 3’ to 5’ of the mRNA sequence)
what does the anticodon do
recognizes codon of mRNA and then the corresponding amino acid is covalently attached to the 3’ OH end of tRNA
aminoacyl-tRNA sythetase
‘charges’ tRNAs with amino acid.
- amino acid + tRNA bonded by acyl linkage/bond VERY high energy
- tRNA binds to its codon in mRNA
result: amino acid is selected by its codon
ribosome
protein synthesis organelle of the cell made up of RNA and proteins. most exist in cytosol but specialized others are attached to the ER. RNA does most of the work (protein is just there for structure)
exit cite
site where tRNAs that have donate their amino acid exit the ribosome
peptidyl site
makes peptide bond (from acyl bond) + binds the tRNA’s attached amino acid with the growing amino acid chain attached
aminoacyl site
where ‘charged’ tRNA enters the ribosome in protein sythesis
how does ribosome find/form around the right spot of mRNA?
bacterial mRNA has a ribosomal bonding site.
eukaryotic mRNA has a 5’ cap (put on during capping, before splicing) that is recognized by proteins that recruit ribosome
translation innitiation
initiator tRNA always carries methionine which recognizes the AUG sequence as start codon
- met-tRNA and small subunits are recruited at cap of mRNA by eukaryotic initiation factores e(IFs). THIS IS TO START BUILDING RHIBOSOME
translation termination (stop codons are not regonized by tRNA)
release factors bind to stop codon and catalize the hydrolosis of the polypeptide from the last tRNA, then ribosomal subunits (the proteins that make it up) dissacociate
polysome
a complex of multiple ribosomes on a single mRNA strand (closed circle model of translation, more efficient and can produce many of the same sequence of proteins at the same time)
