What is the term for the three-nucleotide sequence on tRNA that complements the mRNA codon?
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anticodon
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What is the term for the three-nucleotide sequence on tRNA that complements the mRNA codon?
anticodon
What is the term for the process of charging a specific tRNA with its corresponding amino acid?
recognition and attachment (charging)
Is the genetic code overlapping or nonoverlapping?
nonoverlapping
How many tRNA molecules are required for the organelle-specific changes in genetic code in mitochondria?
22
What is the energy requirement for the formation of one peptide bond during protein synthesis?
The equivalent of the hydrolysis of two ATP molecules to ADP and of two GTP molecules to GDP, or the hydrolysis of four high-energy phosphate bonds.
What is the result of an acceptable missense effect?
The resulting protein molecule may not be distinguishable from the normal one.
What is the result of an unacceptable missense effect?
The protein molecule will not be capable of functioning normally.
What is the site of attachment of the specific amino acid in tRNA?
The acceptor arm, located at the 3′-hydroxyl adenosyl terminal, is the site of attachment of the specific amino acid.
What are the three phases of protein synthesis?
Initiation, Elongation, & Termination
What is the role of the Poly(A) Tail in initiation of protein synthesis?
The poly(A) tail stimulates recruitment of the 40S ribosomal subunit to the mRNA through a complex set of interactions.
What is the degeneracy of the genetic code mostly attributed to?
The degeneracy of the genetic code resides mostly in the last nucleotide of the codon triplet, suggesting that the base pairing between this last nucleotide and the corresponding nucleotide of the anticodon is not strictly by the Watson-Crick rule.
What is the function of the 43S preinitiation complex in protein synthesis initiation?
It binds to the mRNA to form the 48S initiation complex
What is responsible for the 'rough' appearance of the endoplasmic reticulum as seen by electron microscopy?
Attachment of the particulate polyribosomes
What is the term for the ability of the pairing of the codon and anticodon to 'wobble' at a specific nucleotide-to-nucleotide pairing site?
This is called wobble.
What is the role of eIF-2 in protein synthesis initiation?
It consists of α, β, and γ subunits and is phosphorylated by various protein kinases under stress conditions to regulate protein synthesis
What is the most preferred sequence surrounding the AUG initiation codon?
The presence of a purine (Pu) at positions −3 and a G at position +4.
What is the function of eIF-3 in protein synthesis initiation?
It binds with high affinity to the 4G component of 4F and links this complex to the 40S ribosomal subunit
What is the result of the binding of the 60S ribosomal subunit to the 48S initiation complex?
The rapid association of the 40S and 60S subunits to form the 80S ribosome.
What is the role of the cap-binding protein complex, eIF-4F, in protein synthesis initiation?
It binds to the mRNA cap and facilitates the association of mRNA with the 43S preinitiation complex
What is the role of EF1A in the binding of aminoacyl-tRNA to the A site?
EF1A forms a ternary complex with GTP and the entering aminoacyl-tRNA, allowing the correct aminoacyl-tRNA to enter the A site with the release of EF1A • GDP and phosphate.
What is the function of ferritin in response to environmental threats?
Prevents ionized iron (Fe2+) from reaching toxic levels within cells
What is the process called that translates the nucleotide sequence of an mRNA into the sequence of amino acids of a specific protein?
translation
What is the term for the series of codons in an mRNA molecule that specify the amino acid sequence of the encoded protein?
genetic code
How many distinct codons are required for the synthesis of the cellular complement of proteins?
at least 20
What is the result of most single-base changes in the genetic code?
The replacement of one amino acid by another with rather similar functional groups.
What is the name of the enzymes required for the recognition and attachment of amino acids to specific tRNA molecules?
aminoacyl-tRNA synthetases
How many amino acids per second can a eukaryotic ribosome incorporate?
As many as six amino acids per second.
What are the characteristics of the genetic code?
degenerate, unambiguous, nonoverlapping, without punctuation, and universal
What is the role of releasing factor RF1 in termination of protein synthesis?
Recognizes that a stop codon resides in the A site and is bound by a complex consisting of releasing factor RF3 with bound GTP.
What may result from the appearance of a nonsense codon during translation?
The premature termination of translation and the production of only a fragment of the intended protein molecule.
What is the term for codons that do not code for specific amino acids and are utilized as termination signals?
nonsense codons
What results from the deletion of a single nucleotide from the coding strand of a gene?
An altered reading frame in the mRNA.
What is the 4F complex responsible for in protein translation?
The 4F complex is responsible for recognition of the mRNA cap structure, a rate-limiting step in translation.
What is the molecular explanation for the degeneracy of the genetic code?
recognition of specific codons in the mRNA by the tRNA adapter molecules dependent upon the tRNA anticodon region and specific base pairing rules
What happens if three nucleotides or a multiple of three nucleotides are deleted from a coding region?
Translation of the corresponding mRNA will generate a protein that is missing the corresponding number of amino acids.
What are the two types of single-base changes (point mutations)?
The two types of single-base changes are transitions and transversions.
What results from the insertion of one or two or nonmultiples of three nucleotides into a gene?
The reading frame is distorted upon translation, and the same effects that occur with deletions are reflected in the mRNA translation.
What may occur when a different amino acid is incorporated at the corresponding site in the protein molecule due to a single-base change in the mRNA?
A missense effect will occur when a different amino acid is incorporated at the corresponding site in the protein molecule.
What is the role of eIF-4E in the rate of protein translation?
eIF-4E is responsible for recognition of the mRNA cap structure, a rate-limiting step in translation.
How many distinct proteins have been suggested to reside exclusively or extensively within P bodies?
Over 35 distinct proteins
How do poliovirus and other picornaviruses gain a selective advantage in protein synthesis?
By disrupting the function of the 4F complex and promoting the dephosphorylation of BP1 (PHAS-1)
What are P bodies?
Small dense compartments that incorporate mRNAs as mRNPs
What factors result in the phosphorylation of 4E on Ser209 (or Thr210)?
Insulin and other growth factors
What is the function of P bodies?
P bodies are sites of translation repression and mRNA decay
What is the function of 4E-BP1 in translation initiation?
4E-BP1 binds with high affinity to 4E, preventing 4E from binding to 4G and inhibiting translation initiation.
What is the role of elongation factors (EFs) in the process of elongation?
Elongation factors (EFs) catalyze several steps in elongation, including binding of aminoacyl-tRNA to the A site, peptide bond formation, translocation of the ribosome, and expulsion of the deacylated tRNA.
What catalyzes the reaction of peptide bond formation during elongation?
Peptidyl transferase, a component of the 28S RNA of the 60S ribosomal subunit, catalyzes the reaction of peptide bond formation.
