Transcription and Translation (Shiio) Flashcards
DNA –> RNA
Transcription
Transcription is catalyzed by ________ mostly in _______ (also in ______)
- RNA polymerase
- nucleus
- mitochondria
3 types of RNA
mRNA (messenger), rRNA (ribosomal), tRNA (transfer)
Messenger RNA
Template for translation (protein synthesis)
Transfer RNA
Reads the genetic code in mRNA and transfers the appropriate amino acid to a growing polypeptide chain during translation
Ribosomal RNA
component of ribosome (cellular machinery for translation)
Transcription is ____-dependent synthesis of ____ by ________.
- DNA
- RNA
- RNA polymerase
Transcription occurs in the _____ direction, like DNA polymerase.
5’ to 3’
Unlike DNA polymerases, RNA polymerases do not require a ______.
Primer
_____ base pairs with adenine (A), just as thymine (T) does in DNA.
Uracil (U)
RNA polymerase binds to a specific DNA sequence called ________
and initiates transcription.
Promoter
Inhibitors of transcription
- Actinomycin D
- Rifampicin (Rifampin)
Actinomycin D
- Inserts into double-helical DNA and prevents the movement of polymerase along the template DNA
- Inhibits both prokaryotic and eukaryotic transcription
- Used for chemotherapy of a variety of cancers
Rifampicin (Rifampin)
- Inhibits prokaryotic transcription by binding to prokaryotic RNA polymerase
- Used to treat tuberculosis (Mycobacterium infection)
Most eukaryotic mRNAs have a _____ at the 5’ end
and a ______ at the 3’ end
- 5’ cap
- poly(A) tail
Splicing removes _____ from mRNAs in eukaryotes
Introns
Sequences removed by splicing
Introns
Sequences retained after splicing
Exons
Addition of 5’ cap, splicing, and addition of poly(A) tail all occur in the _______.
Nucleus
________ produces DNA from RNA
Reverse transcriptase
Reverse transcriptase allows the synthesis of
DNA complementary to an mRNA template,
which is called ________.
Complementary DNA (cDNA)
cDNA synthesis by reverse transcriptase is
commonly used to _________.
Clone cellular genes
A set of 3 nucleotides (“_____”) codes for a specific amino acid 4 x 4 x 4 = 64 different codons
codon
Protein synthesis usually starts at an N-terminal methionine encoded by ___ and stops at one of the stop codons (___, ___, or ___).
- AUG
- UAA, UAG, UGA
Codons are read by transfer RNAs (tRNAs), using _______, which are complementary to codons.
anticodons
____ insert appropriate amino acids to a growing polypeptide chain during translation
tRNAs
The same amino acid can be encoded by more than one codons (e.g. UUA, UUG, CUU, CUC, CUA, and CUG all encode leucine). the genetic code is “________.”
Degenerate
Mutation that codes for the same amino acid
Silent mutation
Mutation that codes for a different amino acid
Missense mutation
Mutation that codes for a stop codon and results in premature termination
Nonsense mutation
Mutation that inserts or deletes a nucleotide which changes the reading frame
Frameshift mutation
The genetic code is __________, with some minor deviations in mitochondria and a few single-celled organisms.
universal in all species
Q1. Which of the following is a pyrimidine base that is present in RNA but is NOT present in DNA? A. Uracil B. Guanine C. Thymine D. Adenine E. Cytosine
A. Uracil
Q2. Transcription is the cellular process of making
A. new DNA.
B. RNA from DNA.
C. proteins from amino acids by way of RNA.
D. none of the above.
B. RNA from DNA.
Q3. Polyuridylic acid in a cell-free system capable of protein synthesis results in production of polyphenylalanine. In this system, polyuridylic acid functions as A. DNA. B. transfer RNA. C. messenger RNA. D. ribosomal RNA. E. mitochondrial RNA
C. messenger RNA.
Q4. Which of the following statements about transcription is correct?
A. Transcription occurs in the 3’ to 5’ direction.
B. Like DNA polymerases, RNA polymerases need a primer.
C. Transcription usually occurs in the cytoplasm.
D. Transcription starts from a promoter.
E. Actinomycin D enhances transcription.
D. Transcription starts from a promoter.
Q5. A 23-year-old female presents with complaints of difficulty in opening her mouth and a low-grade fever of several days’ duration. The medical history indicates a recent positive PPD skin test (= test for tuberculosis), and the patient is taking rifampin (Rifadin®). The external oral exam shows diffuse swelling at the angle of the right mandible and lateral neck. Oral exam shows gingival swelling and erythema around partially erupted Tooth #32.
Rifampin (Rifadin®) is effective in treating active tuberculosis because it targets which of the following pathways? A. Mitosis B. Replication C. Translation D. Transcription E. mRNA splicing
D. Transcription
Q6. Which of the following statements about RNA processing is correct?
A. Most eukaryotic mRNAs have a cap structure at the 5’ end.
B. Most eukaryotic mRNAs have a poly(A) tail at the 3’ end.
C. Splicing removes introns from mRNAs in eukaryotes.
D. Addition of cap, splicing, and addition of poly(A) tail all occur in the nucleus.
E. All of the above.
E. All of the above.
Q7. What is the biological significance of the extensive degeneracy
of the genetic code?
A. Alters the amino acid sequence of proteins encoded by the DNA.
B. Minimizes the deleterious effect of mutations
C. Maximizes the beneficial effect of mutations
D. Increases chain termination
E. Leads to active proteins
F. None of the above
B. Minimizes the deleterious effect of mutations
Q8. If the anticodon on transfer-RNA is 5’ ACG 3’, then which of the following is its corresponding codon on messenger-RNA?
A. 5’ CGT 3’ B. 5’ UGC 3’ C. 5’ TGC 3’ D. 5’ UAG 3’ E. 5’ CGU 3’
E. 5’ CGU 3’
RNA –> Protein
Translation
Protein synthesis (translation) occurs on the ______, which consist of proteins and ribosomal RNAs (rRNAs).
Ribosomes
Ribosomal subunits and total for prokaryotes
50S + 30S = 70S
Ribosomal subunits and total for eukaryotes
60S + 40S = 80S
Ribosomes are synthesized in the _____.
Nucleolus
Ribosome and mRNA meet in the _______, where protein synthesis occurs.
Cytoplasm
__________ attach the correct amino acids to their tRNAs.
Aminoacyl tRNA synthetases
A ________ is a complex of mRNA and multiple ribosomes for efficient translation.
Polysome
Antibiotics that inhibit prokaryotic translation
- Streptomycin
- Tetracyclin
- Chloramphenicol
- Erythromycin
A toxin that inhibits eukaryotic translation
Diphtheria toxin
A ________ directs proteins to various cellular locations
Signal sequence
Proteins intended for secretion are synthesized on the ribosomes which are __________.
Attached to the endoplasmic reticulum (ER).
Proteins intended for secretion are transported from the ER to the ______ then secreted to extracellular space.
Golgi apparatus
Nuclear proteins are imported to the nucleus using the _________.
Nuclear localization signal (NLS)
______ degradation: Proteins are tagged with _______ and are degraded in the ________.
- Proteasomal
- Poly-ubiquitin
- Proteasome
_______ degradation: Proteins are degraded by proteases in an acidic organelle called _______
- Lysosomal
- Lysosome
Gel electrophoresis separates molecules by ______.
Charge and size
Southern blotting
DNA
Northern blotting
RNA
Western blotting
Protein
Q1. The process by which genetic information flows from RNA to protein is
A. mutation.
B. replication.
C. translation.
D. transcription.
C. translation
Q2. Which of the following statements concerning protein synthesis is correct?
A. Protein synthesis occurs on the ribosomes in the cytoplasm.
B. tRNAs insert appropriate amino acids to a growing polypeptide chain during translation.
C. Eukaryotic ribosomes are composed of 40S and 60S subunits.
D. A complex of mRNA and multiple ribosomes is called a polysome.
E. Tetracycline inhibits prokaryotic protein synthesis.
F. All of the above
F. All of the above
Q3. Which of the following enzymes or processes ensures that the correct amino acid is incorporated for a particular codon during protein synthesis?
A. Amino Acyl-tRNA synthetase B. Ribosomal protein synthesis C. Post-transcription splicing D. RNA synthetase E. Helicase
A. Amino Acyl-tRNA synthetase
Q4. The termination of synthesis of a polypeptide is believed to involve
A. nonsense codons. B. anticodon-codon interaction. C. tRNA which cannot bind amino acids. D. hydrolysis of messenger RNA. E. none of the above.
A. nonsense codons.
Q5. Streptomycin is an antibiotic which inhibits the process of
A. translation in eukaryotes. B. translation in prokaryotes. C. transcription in eukaryotes. D. transcription in prokaryotes. E. DNA replication in prokaryotes.
B. translation in prokaryotes.
Q6. Which of the following represents the mechanism of action of diphtheria toxin?
A. Activates cAMP B. Causes cytolysis C. Inhibits translation D. Inhibits transcription E. Inhibits DNA replication
C. Inhibits translation
Q7. Production of Diphtheria toxin by Corynebacterium diphtheriae requires which of the following genetic processes?
A. Mutation
B. Conjugation
C. Transformation
D. Lysogenic conversion
D. Lysogenic conversion
Q8. Which of the following statements concerning protein targeting
is correct?
A. A signal sequence plays an important role in protein targeting.
B. Proteins intended for secretion are synthesized on ribosomes attached
to the endoplasmic reticulum.
C. Proteins are transported from ER to Golgi before secretion.
D. Proteins in the nucleus are imported through the nuclear pores using nuclear localization signal.
E. All of the above.
E. All of the above.
Q9. Each of the following is involved in protein degradation EXCEPT one.
Which one is the EXCEPTION?
A. Poly-ubiquitin B. Lysosome C. Proteases D. RNA polymerases E. Proteasome
D. RNA polymerases
Q10. Gel electrophoresis is used to separate molecules by A. shape B. charge C. viscosity D. mass and shape E. charge and size
E. charge and size
Q11. Which of the following type of blotting can be used to identify DNA restriction fragments?
A. Eastern
B. Southern
C. Northern
D. Western
B. Southern
