Translation and Regulation Questions and Answers

Q: Which of the following is a nontranslated sequence located between the transcription and the translation start site?

Correct answer: Leader sequenceThe leader (5’ untranslated region) lies between the transcription start and the start codon. It is transcribed but not translated, and it carries the ribosome binding site - the Shine-Dalgarno sequence in bacteria. The corresponding untranslated stretch after the stop codon is the trailer.

Q: Which of the following molecules catalyses the transpeptidation reaction?

Correct answer: Peptidyl transferasePeptidyl transferase forms the peptide bond, transferring the growing chain from the tRNA in the P site to the amino acid in the A site. It is part of the large subunit - and remarkably, the catalytic activity resides in the rRNA, not in the ribosomal proteins, so the ribosome is a ribozyme.

Q: Which of the following acts as the blueprint or template for the process of protein synthesis that takes place on ribosomes?

Correct answer: mRNAMessenger RNA is the working copy of the gene, and the ribosome reads its codons in order to assemble the polypeptide - so it is the template. DNA is the master copy that never leaves the nucleus in eukaryotes; tRNA brings the amino acids; rRNA builds and works the ribosome.

Q: The interaction between mRNA and tRNA determines the position of amino acid in a polypeptide sequence. This is called the

Correct answer: adaptor hypothesisCrick’s adaptor hypothesis proposed that an amino acid cannot recognise a codon directly, so an adaptor molecule must exist that binds the amino acid at one end and pairs with the codon at the other. tRNA turned out to be exactly that. The wobble hypothesis, also Crick’s, is a separate idea about the third base of the codon.

Q: How many codons are there in the genetic code ?

Correct answer: 64The code reads three bases at a time from four possible bases, giving \(4^3 = 64\) codons. Of these, 61 specify amino acids and three are stop codons.

Q: In database management system, an executing program that reads or updates records stored in the database is called a

Correct answer: transactionA program that reads or updates stored records is a transaction as far as the DBMS is concerned - a unit of work to which the ACID guarantees apply. Treating it as a unit is what lets the system make it atomic and isolate it from others running at the same time.

Q: Which of the following contains a complete record of all activity that affected the contents of a database during a certain period of time?

Correct answer: transaction logThe transaction log is the complete record of everything that affected the database over a period - every transaction, what it did, and when. It is what makes recovery possible, and it is also the audit trail.

Q: In this instance, dirty reads are disallowed, while nonrepeatable reads and phantom reads are allowed.

Correct answer: Read committedRead committed guarantees only that data read has been committed by someone, so dirty reads are impossible. It takes no long-term read locks, so a row may change between two reads within the same transaction - a non-repeatable read - and new rows may appear, a phantom. It is the default level in most systems, as a compromise between correctness and concurrency.

21.

Which binding is inhibited by pactamycin?

A.Aminoacyl-tRNA to the A-site of 30S subunit
B.Initiator-tRNA to 30S/40S initiation complexes
C.Peptidyl t-RNA to the 50S subunit
D.Formation of peptide bond in P site

Answer: B

Correct answer: Initiator-tRNA to 30S/40S initiation complexes

Pactamycin blocks initiation: it prevents the initiator tRNA from binding to the small subunit initiation complex, so no ribosome can start reading the message. Because it acts before elongation begins, ribosomes already engaged run to the end and come off - which is why the drug is used experimentally to clear the message of ribosomes.

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22.

Which of the following is a nontranslated sequence located between the transcription and the translation start site?

A.Ending frame
B.Leader sequence
C.Trailer sequence
D.Reading frame

Answer: B

Correct answer: Leader sequence

The leader (5’ untranslated region) lies between the transcription start and the start codon. It is transcribed but not translated, and it carries the ribosome binding site - the Shine-Dalgarno sequence in bacteria. The corresponding untranslated stretch after the stop codon is the trailer.

Discuss in Forum

23.

Which of the following molecules catalyses the transpeptidation reaction?

A.RNA polymerase
B.Peptidyl transferase
C.DNA ligase
D.DNA polymerase

Answer: B

Correct answer: Peptidyl transferase

Peptidyl transferase forms the peptide bond, transferring the growing chain from the tRNA in the P site to the amino acid in the A site. It is part of the large subunit - and remarkably, the catalytic activity resides in the rRNA, not in the ribosomal proteins, so the ribosome is a ribozyme.

Discuss in Forum

24.

Which of the following acts as the blueprint or template for the process of protein synthesis that takes place on ribosomes?

A.rRNA
B.DNA
C.tRNA
D.mRNA

Answer: D

Correct answer: mRNA

Messenger RNA is the working copy of the gene, and the ribosome reads its codons in order to assemble the polypeptide - so it is the template. DNA is the master copy that never leaves the nucleus in eukaryotes; tRNA brings the amino acids; rRNA builds and works the ribosome.

Discuss in Forum

25.

The interaction between mRNA and tRNA determines the position of amino acid in a polypeptide sequence. This is called the

A.degeneracy
B.Wobble hypothesis
C.promiscuity
D.adaptor hypothesis

Answer: D

Correct answer: adaptor hypothesis

Crick’s adaptor hypothesis proposed that an amino acid cannot recognise a codon directly, so an adaptor molecule must exist that binds the amino acid at one end and pairs with the codon at the other. tRNA turned out to be exactly that. The wobble hypothesis, also Crick’s, is a separate idea about the third base of the codon.

Discuss in Forum

26.

How many codons are there in the genetic code ?

A.20
B.61
C.64
D.72

Answer: C

Correct answer: 64

The code reads three bases at a time from four possible bases, giving \(4^3 = 64\) codons. Of these, 61 specify amino acids and three are stop codons.

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27.

In database management system, an executing program that reads or updates records stored in the database is called a

A.conceptualization
B.execution
C.implementation
D.transaction

Answer: D

Correct answer: transaction

A program that reads or updates stored records is a transaction as far as the DBMS is concerned - a unit of work to which the ACID guarantees apply. Treating it as a unit is what lets the system make it atomic and isolate it from others running at the same time.

Discuss in Forum

28.

Which of the following contains a complete record of all activity that affected the contents of a database during a certain period of time?

A.report writer
B.query language
C.data manipulation language
D.transaction log

Answer: D

Correct answer: transaction log

The transaction log is the complete record of everything that affected the database over a period - every transaction, what it did, and when. It is what makes recovery possible, and it is also the audit trail.

Discuss in Forum

29.

Chloramphenicol inhibits protein synthesis by acting on which target ?

A.The 30S subunit, blocking tRNA binding
B.The 50S subunit, inhibiting peptidyl transferase
C.The sigma factor of RNA polymerase
D.The cell wall precursor pathway

Answer: B

Correct answer: The 50S subunit, inhibiting peptidyl transferase

Chloramphenicol binds the 50S subunit and blocks the peptidyl transferase centre, so no peptide bond forms. It is bacteriostatic, and because mitochondrial ribosomes are also 70S it carries a risk of bone marrow toxicity.

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30.

In this instance, dirty reads are disallowed, while nonrepeatable reads and phantom reads are allowed.

A.Read committed
B.Read uncommitted
C.Repeatable read
D.Serializable

Answer: A

Correct answer: Read committed

Read committed guarantees only that data read has been committed by someone, so dirty reads are impossible. It takes no long-term read locks, so a row may change between two reads within the same transaction - a non-repeatable read - and new rows may appear, a phantom. It is the default level in most systems, as a compromise between correctness and concurrency.

Discuss in Forum

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