Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
30 Cards in this Set
- Front
- Back
|
There are how many different codons?
|
64.
61 code for the 20 common amino acids. Codons UAG, UGA, and UAA are termination codons and stop translation |
|
|
What are Characteristics of the Genetic Code?
|
Specificity – A specific codon always codes for the same amino acid.
Universality – The genetic code has been conserved through evolution. Redundancy (Degeneracy) – An amino acid might have more than one codon coding for it. Nonoverlapping – Read as a continuous sequence of bases |
|
|
What are the three types of point mutations?
|
Silent mutation – The codon with the changed base still codes for the same amino acid.
Missense mutation – The altered nucleotide base causes a different amino acid to be coded. Nonsense mutation – The altered base causes the codon to be a termination codon |
|
|
What is a frame-shift mutation?
|
one or two nucleotide bases has been deleted or added
The amino acid sequence becomes radically different |
|
|
What are Splice Site Mutations?
|
Alter the way in which introns are removed from pre-mRNA molecules, producing aberrant proteins
|
|
|
Myotonic dystrophy gene silencing is the result of...
|
splicing alterations
|
|
|
When a codon is repeated multiple times in a gene it is called...
|
A Tandem Repeat
|
|
|
Huntington disease and Fragile-X syndrome are the result of...
|
Tandem Repeats
Huntington: Extra glutamine residues |
|
|
What is the function of Aminoacyl-tRNA synthetases?
|
Attach an amino acid to its corresponding tRNA (on the 3' end) with a covalent bond.
Requires ATP |
|
|
What is the Wobble hypothesis?
|
A tRNA can recognize more than one codon for a specific amino acid.
The movement of the first nucleotide base in the anticodon allows for nontraditional base pairing. |
|
|
What does it mean for mRNA to be Polycistronic?
|
prokaryotic mRNA often has several coding regions
Each coding region has its own initiation codon and produces a separate polypeptide |
|
|
What happens during initiation of translation?
|
The individual components come together:
Two ribosomal subunits mRNA to be translated Aminoacyl-tRNA specified by the first codon. GTP Initiation factors: IF-1, IF-2, and IF-3 in prokaryotes At least 9 eIF’s in eukaryotic translation |
|
|
What is a Shine-Dalgarno sequence?
|
Located on the mRNA – upstream of the AUG start codon.
Used for recognition and attachment of the mRNA to the 16S rRNA of the ribosome. The mRNA and the 16S rRNA form complementary base pairs |
|
|
AUG is the ___________ codon
|
initiation
|
|
|
In prokaryotes, the initiator tRNA carries an _________ methionine to start the polypeptide chain.
|
N-formylated
In eukaryotes, the methionine is not formylated |
|
|
How does streptomycin inhibit bacterial translation?
|
Binds to the 30S subunit and distorts its structure, preventing initiation.
|
|
|
How do tetracyclines inhibit bacterial translation?
|
Interact with small ribosomal subunits, blocking access of the aminoacyl-tRNA to the mRNA-ribosome complex.
|
|
|
How does puromycin inhibit bacterial translation?
|
Bears a structural resemblance to aminoacyl-tRNA and becomes incorporated in to the growing peptide chain, stopping elongation.
In both prokaryotes and in eukaryotes. |
|
|
How does chloramphenicol inhibit bacterial translation?
|
Inhibits prokaryotic peptidyltransferase.
|
|
|
In prokaryotes, initiation factors are released when?
|
When the 50S subunit arrives to form the 70S initiation complex
|
|
|
What is the function of elongation factors?
|
Direct the binding of the appropriate tRNA to the codon in the empty A-site.
|
|
|
What is peptidyltransferase?
|
A component of the 50S subunit (23S RNA). It transfers the amino acid from the P-site onto the amino acid at the A-site, and catalyzes peptide bond formation.
|
|
|
Which rRNA molecule is a ribozyme?
|
23S rRNA
|
|
|
During elongation, what happens after the peptide bond is formed?
|
The ribosome advances three nucleotides down on the mRNA.
EF-G and GTP are required The uncharged tRNA is released The peptidyl-tRNA moves from the A site to the P site. |
|
|
What are UGA, UAA, and UAG?
|
termination codons
|
|
|
Termination codons are recognized by what?
|
Recognized by release factors: RF-1 and RF-2.
RF-3 binds GTP and stimulates the activity of RF-1 and RF-2. |
|
|
How do clindamycin and erythromycin inhibit prokaryotic translation?
|
Bind irreversibly to a site on the 50S subunit of the bacterial ribosome, inhibiting translocation.
|
|
|
How does the diptheria toxin inhibit eukaryotic translation?
|
Inactivates the eEF-2 elongation factor, preventing translocation.
|
|
|
When multiple ribosomes are translating a single mRNA the complex is called...
|
A Polysome.
only present in eukaryotes. |
|
|
What is a Zymogen?
|
inactive precursor of secreted enzyme
|
