SBI4U - Protein Synthesis
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Describe the Beadle and Tatum experiment
- Neurospora grows on a minimal medium with sugars and salts
- and whatever
- In order to grow on these mediums, enzymes must be made to
- convert the salt sugar whatever into amino acids and vitamins
- If the genes that make an enzyme were mutated, the bacterium
- should not grow on the minimal medium. gene a is fucked up, so enzyme a is
- fucked up, so no growth
- Xrays cause mutations, so they took neurospora and make it
- touch x rays to get mutants, got the
- offspring, made it live in a medium containing all the vitaminds and amino
- acids (complete), and then a minimal medium. Most of them in minimal mediums
- grew but one, from that one they tried making it grow in a single vitamin and
- single amino acid culture. The medium grew in the vitamin, so then thye did
- single vitamins to see which vitamin it was lacking. It grew on the B6 vitamin,
- meaning that it could not make vitamin B6 as one of the enzymes in the B6
- synthesis pathway must have been affected, therefore the gene must have been
- mutated by xrays. When the vitamin was provided, the culture grew
What did Vernon discover?
Linked abnormality of Sickle Cell to a single alteration in amino acid sequence of hemoglobin
What is the purpose of mRNA?
At the end of transcription, mRNA carries the genetic info from the DNA out to the cytoplasm to begin translation.
- This is the end product of transcription
- Varies in length
What is the purpose of rRNA
Ribosomal RNA binds with proteins to make ribosomes
What is the purpose of tRNA
- Carries Amino Acid to the site of protein synthesis
- Clover lead shape
What is the start codon?
What is the stop codon?
UAA, UGA, UAG
Who discovered the first codon?
Marshall Mirenburg found the first codon, UUU
What are the stages for transcription and translation?
- Post transcriptional/translational modification
INITIATION FOR TRANSCRIPTION
RNA polymerase binds DNA at the promoter site rich in A-T bc only 2 H bonds to open the double helix to expose the template strand
INITIATION FOR TRANSLATION
Ribosome moves along mRNA until start codon is in the P site
ELONGATION FOR TRANSCRIPTION
RNA polymerase transcribes for 5 to 3, synthesizing the template strand to create mRNA.
Does not need a primer like DNA replication
What does the mRNA identical to, DNA or coding strand
Coding strand, complementary to the DNA strand
TERMINATION FOR TRANSCRIPTION
RNA polymerase continues to transcribe until it hits a stop codon slash terminator sequence of a gene
When it does, RNA polymerase breaks off and transcription stops
POST TRANSCRIPTIONAL MODIFICATION
only pre-mRNA is made! you have to modify it or else enzymes will eat it as it leaves nucleus
post transcriptional modification occurs in two ways: capping and tailing, and removing junk
to cap and tail, 5' and 3' tail is added to protect primary transcript from nucleases and phosphatases
removing junk = removing introns and joining exons using the enzyme splicesosomes
why does mRNA have to go through post transcriptional modification?
you have to modify it or else enzymes will eat it as it leaves nucleus
What is the 5' cap?
What is a ribosome for?
- small subunit: binding site of mRNA (carries genetic info from DNA to cytoplasm)
- larger subunit: three binding sites of tRNA (transfers AA to site of protein synthesis)
Describe the anatomy of a tRNA molecule
- cloverleaf shape
- each tRNA specific for one AA
How many different tRNAs are there?
45, 3 of them are stop
What does the aminoacyl-tRNA do?
Acyl = carboxylic acid = ions
What does aminoacyl-tRNA synthetase do?
enzyme; attaching AA to RNA molecule
ELONGATION FOR TRANSLATION
three binding sites, = three elongation sections
1) A - acceptor site - codon recognition - woth the 2nd codon in the P site, an incoming charged tRNA molecule will bring the second AA to the A site
2) P - peptidyl site - peptide bone formation - ribosomes make a peptide bond
3) E - exit site - translocation - ribosomes shift the codon, everything moves down
What enzyme helps the addition of the 3' tail?
poly-A polymerase; poly-A tail
describe the function of the arms of tRNA
One arm has the anticodon regions, one arm carries the actual amino acid.
TERMINATION OF TRANSLATION
Similar to transcription, when a stop codon occurs in the A site, a "release factor" binds to the stop codon and instead of an AA being formed, water is binded. This hydrolyzes the pp from the tRNA and causes the ribosomal mRNA complex gto me released
- Occurs in smooth er
- Adding phosphates or sugars to protein!
where does post-translation modification occur?
where does post-transcription modification occur?
LOSER THERE IS NO SPECIFIC PLACE OF POST TRANSCRIPTION MODIFICATION LOL PWNED XD
compare transcription and translation!!!! GO!
- transcription: transcribes genes into mRNA
- translation: manufacture a protein from mRNA
- initiation transcription: RNA polymerase binds to DNA promoter site
- initiation translation: ribosome moves along mRNA until it hits a start codon
- elongation transcription: template strand, nucleotides lay along it to form mRNA
- elongation translation: tRNA recognizes the AA and the mRNA. codon starts on 2nd site so another AA is added to the A site, peptide bond forms, moves down
- termination transcription: stop codon
- termination translatio: stop codon, water is added instead of AA, hydrolyzes ppp off the ribosome
- post-transcription: capping and tailing, removing junk
- post-translation: glycosylation and phosphorylation
why is gene regulation important?
save energy of cell, no waste
how does transcription affect gene regulation?
picks the genes to be transcribed
how does post-transcription affect gene regulation?
introns removed and exon put together
how does translation affect gene regulation?
controls how often and rapid mRNA transcripts into proteins. controls change in time for mRNA to be activated and change of speed of cytoplasmic enzymes to destroy RNA
basically how much and how fast mRNA is translated to proteins
how does post-translation affect gene regulation?
affect its functionality; rate of protein to be functional and time it remains functional
name the scenarios where a negative gene regulator is necessary
1) no lactose is present repressor gene attaches itself to operator so RNA polymerase cant bind, genes of operon cant work, negatve
2) lactose presentlactose binds to repressorrepressed cant attach to operatorRNA polymerase can bind to promotor genes transcribedenzymes produced
what is a negative gene regulator?
a protein molecule that interacts dirently with a genome to turn off gene regulation
negative gene regulation is how the protein affects gene expression
what is a promotor?
where rna polymerase binds
where does rna polymerase bind in an operon?
what is an operator?
repressor protein binds here
repressor protein binds where
what is an operon
stretch of dna that contains a set of 1 or more genes involved in a particular metabolic pathwar
name the scenario where a positive gene regulator is necessary
lactose and glucose are available! so glucose is used
what happens if no glucose is available?
cAMP accumulates, binds with activator, those two bind to promotor, making it easier for RNA polymerase to bind to promotor, transcriptions will be FASTAAAHHH YAY POSITIVE
what are the two groups of mutations?
- point mutations (affects one or a few nucleotides)
- chromosomal mutations (affects multiple genes)
what are two groups of point mutations?
- nucleotide substitution (replacement of one nucleotide for another)
- frameshift mutation (insertion or deletion)
detriments of nucleotide substitutions?
- silent - redundant, yolo
- nonsense - stop codon or start codon erased
- missense - altered protein but still functional
what are two groups of chromosomal mutations?
causes of mutation?
- spontaneous - molecular, nature
- induced - caused by mutagens
differences b/w pro and eu
- prokaryotes have no nuclear membrane so once RNA polymerase transcribes it can also translate
- eukaryotes arent swagged enough to do this
- prokaryskjhf dont have non coding regions (introns)
- eu do
- pro genome is small and circular, has operones
- eu genome is large and in chromosomes, no operons
- pro translation has formyl-meth
- eu is just meth
- pro translation starts with shine-dalgarno sequence
- eu translation starts with 5' and 3'
why do mitochondria be pro?
- circular genomes
- sequence of dna similar to pro
- fission division!!!!
- mito have their own system of dna synthesis, transcription, and translation
name an example of asn endosymbiotic system
- [2:52:24 AM] thersa ngyen: small biflaggjskfhkj alga and compartment in the alga
- [2:52:29 AM] thersa ngyen: the compartment has chloroplast
- [2:52:30 AM] Kenneth: oh
- [2:52:35 AM] thersa ngyen: so it makes food for alga
Difference between histones and nucleosome?
- histones are positively charged proteins that bidn to DNA in chromosomes
- nucleosomes consist of eight histones enveloped by coiled DNA
what is the sequence in which dna is ordered?
- every 200 nucleotides, dna coiled arounded groups of 8 histones
- nucleosomes coil into chromatin fibres
- fibres fold into final chromatin structure
what is a pseudogene
- dna sequences that are homologous with knowm genes but never tgranscribed
- nucleotide sequence simi,ar to functioning but not expressive
what are sequences that repeat over and oveer?
microsatellietes; variable number tandem repeats (VNTR)
how does RNA Polymerase diff from DNS polermase
RNA doesnt need a rpimer
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