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Who studied Neurospora crassa by creating DNA mutations and seeing if their defective enzymes were inherited?
Beadle & Tatum
What is the type of mutation if a mutated gene is necessary to make a required compound and therefore, would not grow in minimal media?
Nutritional mutation
What is the theory called that one gene is responsible for one enzyme?
One gene/one-enzyme hypothesis
What is the theory described by Francis Crick that information only flows from DNA→RNA→protein?
Central Dogma
What are the 2 exceptions to the central dogma?
Retroviruses (use reverse transcriptase. RNA→DNA→RNA→protein)
Prions (protein→protein)
mRNA produced from transcription used to direct synthesis of polypeptides
Takes place at ribosome
Requires several kinds of RNA
Translation
DNA-directed synthesis of RNA
Only one strand (template strand) of DNA is used
T in DNA replaced by U in RNA
Transcription
Who wanted to prove that codons are blocks of 3 DNA nucleotides which each code for an amino acid?
Crick and Brenner
Code is ____________________, meaning that some amino acids are specified by more than one codon (64 codons, only 20 amino acids). Not uniform
Degenerate
True or false: Code is not universal
False (it is)
Which type of transcription has only one RNA polymerase, which does not need a primer and adds free RNA nucleotides to the 3’ end?
Prokaryotic transcription
What is the template by which the RNA sequence is made?
DNA template strand
What strand has the same nucleotide sequence as the RNA sequence (except U instead of T)?
DNA coding strand
What is the first base to be transcribed into RNA, numbered +1, called?
Start site
What is closer to the 5’ end of the coding strand than the start site, numbered -1,-2, -3, etc?
Upstream
What is closer to the 3’ end of the coding strand than the start site, numbered +1,+2, +3, etc?
Downstream
What two things are necessary in order to properly initiate RNA synthesis?
Core enzyme + sigma factor
What is the enzyme that drives RNA synthesis?
Core enzyme
What helps RNA polymerase recognize the beginning of genes?
Sigma factor
What are the 3 basic steps of prokaryotic transcription?
Initiation
Elongation
Termination
What is a part of prokaryotic initiation of transcription that is a short sequence upstream of start site that forms a recognition and binding site for the RNA polymerase?
Promoter (TTGACA -35 sequence; TATAAT -10 sequence)
One of the conserved sequences within the promoter that indicates site of initiation and direction of transcription
Asymmetrical
First step in prokaryotic initiation of transcription?
-35 sequence binds to sigma subunit
Second step in prokaryotic initiation of transcription?
DNA helix unwinds at -10 sequence
Third step in prokaryotic initiation of transcription?
RNA polymerase binds to the unwound DNA. RNA transcription begins at the start site. Sigma factor released
What is the unwound section of DNA template, where RNA transcription occurs called?
Transcription bubble
The step in prokaryotic transcription where strand grows in 5’→3’ direction as nucleotides are added onto 3’ end. Transcription bubble passes and the now-transcribed DNA is rewound as it leaves bubble.
Prokaryotic Elongation
The step in prokaryotic transcription where specific ______________ sequences are used. RNA transcript is released. RNA polymerase releases DNA. DNA rewinds back into helix
Prokaryotic Termination
With the termination sequences, a series of complementary base pairs will bind to each other to form a __________________
Hairpin
When a single transcription unit encodes multiple enzymes for a particular pathway, which allows them to be regulated together
Operon genes
In eukaryotic transcription, ___ ___ ___ ____________________ transcribes rRNA
RNA polymerase I
In eukaryotic transcription, ___ ___ ___ ____________________ transcribes mRNA
RNA polymerase II
In eukaryotic transcription, ___ ___ ___ ____________________ transcribes tRNA and many other small RNAs
RNA polymerase III
How is eukaryotic transcription initiation different from prokaryotic?
Transcription factors
In eukaryotic transcription initiation, what gets the RNA polymerase II enzyme to a promoter and to initiate gene expression and interacts with RNA polymerase to form initiation complex at promoter?
Transcription factors 2
How is eukaryotic transcription termination different from prokaryotic?
Termination sites not as well defined and RNA transcript is modified after transcription
In eukaryotes, the primary transcript must be modified to become ___________ ______
mature mRNA
What are the 3 ways that eukaryotic pre-mRNA are modified to produce mature mRNA?
Addition of a 5’ cap
Addition of a 3’ poly-A tail
Removal of non-coding sequences
The non-coding sequences are called what?
Introns
The sequences that will be translated are called what?
Exons
What is a complex of snRNA and proteins that recognizes the intron-exon boundaries?
snRNPs (Small ribonucleoprotein particles)
What is a key sequence within an intron that plays a crucial role in RNA splicing that the snRNPs bind to?
Branch site
What is the organelle responsible for removing introns made up of a cluster of snRNPs with other proteins?
Spliceosome
The result of the 5’ end of an intron being cut and attached to branch site
Lariat (lasso)
What is it called when a single primary transcript is spliced into different mature mRNAs that include different sets of exons during splicing?
Alternative splicing
What carries amino acids to the ribosome for incorporation into a polypeptide (protein)?
tRNA
An adapter protein must interact with what two things?
mRNA and amino aicds
Amino aicds ← → _________________ __________
Acceptor stem
mRNA← → _______________ __________
Anticodon loop
Each tRNA must be _____________ with the correct amino aicd on the acceptor stem
Charged
What adds amino acids to the acceptor stem of tRNA in the tRNA charging reaction?
Aminoacyl-tRNA synthetases
Aminoacyl-tRNA synthetases produce what?
Charged tRNA 1
What are the 3 steps in the tRNA charging reaction?
Amino acid is activated. ATP provides energy to bring amino acid to enzyme
tRNA binds to enzyme
Amino acid attaches to tRNA. Charged tRNA is then released
________________ _____ has an amino acid added using the energy from ATP. Can undergo peptide bond formation at ribosome without additional energy
Charged tRNA 2
What are the 2 primary functions of the ribosome?
Decode the mRNA code
Form peptide bonds
What is the enzymatic component of the large subunit of ribosome?
Peptidyl transferase
Which tRNA binding site binds the tRNA that carried the last amino acid?
E site
Which tRNA binding site binds the tRNA attached to the growing peptide chain?
P site
Which tRNA binding site binds the tRNA carrying the next amino acid?
A site
What is the main step in initiation of prokaryotic translation?
Recognition of the start codon (AUG-methionine)
Large subunit now added. Initiator tRNA bound to P site. A site is empty
Initiation of prokaryotic translation
What are the differences between initiation of prokaryotic vs eukaryotic translation?
In eukaryotes, initiating amino acid is methionine (not fMet). More complicated initiation complex. Lack of an RBS-small subunit recognizes and binds to 5’ cap of mRNA
The elongation factor binds to a charged tRNA and brings it to empty A site
1st step in prokaryotic elongation of translation
Peptidyl transferase forms peptide bond. Growing chain cut off P site tRNA and stuck on amino acid of A site tRNA
2nd step in prokaryotic elongation of translation
Translocation of ribosome. tRNA with amino acid chain moved to P site
3rd step in prokaryotic elongation of translation
Addition of successive amino acids occurs as a cycle
4th step in prokaryotic elongation of translation
What allows less stringent pairing between the 3’ base of the codon and the 5’ base of the anticodon?
Wobble pairing
Stop codons are recognized by release factors which release the polypeptide from the ribosome
Termination of prokaryotic translation
In eukaryotes, translation may occur in the _______________ or at the _________ _________________ _________________
Cytoplasm; rough endoplasmic reticulum
Intracellular, cytoplasmic proteins
Cytoplasm
Intramembrane proteins or secreted proteins→ protein trafficking pathway
RER
In order to target protein translation to the RER, what must happen?
The signal sequence at beginning of polypeptide binds to a signal recognition particle
What mutation alters a single base?
Point mutation
What mutation substitutes one base for another?
Base substitution
A type of base substitution where the same amino acid was inserted?
Silent mutation
A type of base substitution that changes the amino acid inserted?
Missense mutation
What mutation changes to stop codon?
Nonsense mutations
What mutation is an addition or deletion of a single base?
Frameshift mutation