Translation and Regulation Questions and Answers

Q: A lock that allows concurrent transactions to access different rows of the same table is known as a

Correct answer: Row-level lockA row-level lock locks only the row being changed, so other transactions may work on different rows of the same table at the same time. It gives the most concurrency of the common granularities, at the cost of more locks to manage; a table-level lock would block the whole table.

Q: The property of a transaction that survives system crashes is

Correct answer: DurabilityDurability guarantees that once a transaction has committed, its changes survive any subsequent failure - power loss, crash, or restart. It is implemented by writing the changes to a log on stable storage before reporting the commit, so that recovery can replay them.

Q: According to the wobble hypothesis, non-standard base pairing occurs at which position of the codon ?

Correct answer: Third positionCrick’s wobble hypothesis holds that pairing between the third base of the codon and the first base of the tRNA anticodon is relaxed. This is why fewer than 61 tRNA species can read all 61 sense codons, and why synonymous codons usually differ in the third position.

Q: The final step of gene expression is protein synthesis, which is also known as

Correct answer: translationTranslation is protein synthesis - the ribosome reading the mRNA codons and assembling the corresponding amino acids. The name reflects the change of language: from the four-letter alphabet of nucleic acid to the twenty-letter alphabet of protein. Transcription is DNA to RNA, and replication DNA to DNA.

Q: The A site of the ribosome is where ________.

Correct answer: the incoming aminoacyl-tRNA bindsThe ribosome has three tRNA sites: A for the arriving aminoacyl-tRNA, P for the tRNA holding the growing peptide, and E through which the discharged tRNA leaves. Each translocation step moves a tRNA one site along.

Q: Which termination codon is called amber?

Correct answer: UAGUAG is amber, UAA is ochre and UGA is opal. The names are historical accidents: amber is a translation of the surname of Harris Bernstein, whose family name means amber in German, and the other two were chosen to match. Amber suppressor mutations - tRNAs that read UAG as an amino acid - became a standard genetic tool.

Q: With regards to transaction processing, any DBMS should be capable of:

Correct answer: All of the above.All three are the ACID guarantees in other words: freedom from interference is isolation, not losing part of a transaction on failure is atomicity and durability, and not leaving the database inconsistent is consistency. A DBMS worth the name provides all of them.

81.

A lock that allows concurrent transactions to access different rows of the same table is known as a

A.Field-level lock
B.Row-level lock
C.Table-level lock
D.Database-level lock

Answer: A

Correct answer: Row-level lock

A row-level lock locks only the row being changed, so other transactions may work on different rows of the same table at the same time. It gives the most concurrency of the common granularities, at the cost of more locks to manage; a table-level lock would block the whole table.

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82.

The property of a transaction that survives system crashes is

A.Atomicity
B.Durability
C.Isolation
D.All of the mentioned

Answer: B

Correct answer: Durability

Durability guarantees that once a transaction has committed, its changes survive any subsequent failure - power loss, crash, or restart. It is implemented by writing the changes to a log on stable storage before reporting the commit, so that recovery can replay them.

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83.

According to the wobble hypothesis, non-standard base pairing occurs at which position of the codon ?

A.First position
B.Second position
C.Third position
D.Both first and second positions

Answer: B

Correct answer: Third position

Crick’s wobble hypothesis holds that pairing between the third base of the codon and the first base of the tRNA anticodon is relaxed. This is why fewer than 61 tRNA species can read all 61 sense codons, and why synonymous codons usually differ in the third position.

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84.

The final step of gene expression is protein synthesis, which is also known as

A.replication
B.translation
C.transcription
D.none of these

Answer: B

Correct answer: translation

Translation is protein synthesis - the ribosome reading the mRNA codons and assembling the corresponding amino acids. The name reflects the change of language: from the four-letter alphabet of nucleic acid to the twenty-letter alphabet of protein. Transcription is DNA to RNA, and replication DNA to DNA.

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85.

A polysome is best defined as ________.

A.a ribosome with several subunits
B.several ribosomes translating one mRNA simultaneously
C.a cluster of tRNA molecules
D.an mRNA carrying several poly-A tails

Answer: A

Correct answer: several ribosomes translating one mRNA simultaneously

A polysome, or polyribosome, is a single mRNA being read at once by many ribosomes spaced along its length. It lets a cell produce many copies of a protein from one transcript, and in bacteria translation of the leading end begins while the far end is still being transcribed.

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86.

The A site of the ribosome is where ________.

A.the incoming aminoacyl-tRNA binds
B.the peptide chain is held during elongation
C.the uncharged tRNA exits
D.the mRNA is unwound

Answer: C

Correct answer: the incoming aminoacyl-tRNA binds

The ribosome has three tRNA sites: A for the arriving aminoacyl-tRNA, P for the tRNA holding the growing peptide, and E through which the discharged tRNA leaves. Each translocation step moves a tRNA one site along.

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87.

The development of global regulatory systems in prokaryotes

A.determines the exact location of the cell on the globe
B.aids in DNA replication
C.determines the exact location of the replication site
D.regulates many genes under varying environmental conditions

Answer: D

Correct answer: regulates many genes under varying environmental conditions

A global regulatory system - a regulon or stimulon - controls many genes at once in response to a single condition: heat shock, starvation, oxygen. Coordinating a whole set of responses through one signal is far more efficient than regulating each gene separately.

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88.

Which termination codon is called amber?

A.UAA
B.UAG
C.UGA
D.AUG

Answer: B

Correct answer: UAG

UAG is amber, UAA is ochre and UGA is opal. The names are historical accidents: amber is a translation of the surname of Harris Bernstein, whose family name means amber in German, and the other two were chosen to match. Amber suppressor mutations - tRNAs that read UAG as an amino acid - became a standard genetic tool.

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89.

____ means that the data used during the execution of a transaction cannot be used by a second transaction until the first one is completed.

A.Consistency
B.Atomicity
C.Durability
D.Isolation

Answer: D

Even though multiple transactions may execute concurrently, the system guarantees that, for every pair of transactions Ti and Tj, it appears to Ti that either Tj finished execution before Ti started or Tj started execution after Ti finished.

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90.

With regards to transaction processing, any DBMS should be capable of:

A.Ensuring that transactions are free from interference from other users.
B.Parts of a transaction are not lost due to a failure.
C.Transactions do not make the database inconsistent.
D.All of the above.

Answer: D

Correct answer: All of the above.

All three are the ACID guarantees in other words: freedom from interference is isolation, not losing part of a transaction on failure is atomicity and durability, and not leaving the database inconsistent is consistency. A DBMS worth the name provides all of them.

Discuss in Forum

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