Question 1

The scientist(s)________ developed the triplet-binding assay.Samples containing ribosomes and a particular RNA triplet were exposed to charged tRNAs with different radiolabeled amino acids.Only the amino acid whose tRNA matched the triplet would bind the ribosome.The triplet-binding assay established relationships between particular triplet sequences and specific amino acids.

Accepted Answer

Marshall Nirenberg and Philip Leder developed the triplet-binding assay, which was crucial in deciphering the genetic code by establishing the relationship between RNA triplets and specific amino acids.

Question 2

What is the minimal number of tRNAs that can be used to recognize all of the codons for threonine?

Accepted Answer

Threonine has codons ACU, ACC, ACA, and ACG. As each codon has a different third base (U, C, A, or G), two tRNAs can recognize all four codons through wobble base pairing.

Question 3

You perform a cell free translation experiment like Nirenberg and Matthaei.You start with 60% C and 40% A.What relative amount of radiolabeled proline do you expect in the translated polypeptides?

Accepted Answer

In the genetic code, proline is coded for by the codon CCx (where x can be any nucleotide). Out of the four possible codons (CCU, CCC, CCA, and CCG), only CCC codes for proline exclusively. Therefore, if the starting mixture has 60% C (which pairs with G to form the CCC codon), then we would expect 60% of the proline residues in the translated polypeptides to be labeled with radiolabeled proline. Since the starting mixture also has 40% A (which pairs with U to form another codon for proline, CCU), we would expect 40% of the proline residues in the translated polypeptides to be unlabeled. Therefore, the relative amount of radiolabeled proline in the translated polypeptides would be 60% of 60%, or 36%.

Question 4

The scientist(s)________ developed a novel method to synthesize RNA.Short RNAs of 2 to 4 nucleotides were linked together to create a copolymer.The resulting peptide created after translation revealed the 3-letter code for the amino acids.

Accepted Answer

Khorana and colleagues developed methods to synthesize RNA sequences, which helped in deciphering the genetic code by linking short RNAs to create copolymers.

Question 5

The scientist(s)________ created a cell-free translation system.An mRNA template was added to a number of tubes,each containing amino acids with a different one radiolabeled.Radiation was measured from the precipitated protein,and this corresponded to the mRNA template that had been added.This was the first experiment that demonstrated the ability to synthesize polypeptides from synthetic mRNA,and revealed a relationship between the two.

Accepted Answer

The experiment described in the question is the classical experiment conducted by Nirenberg and Matthaei in 1961. They created the first cell-free translation system and demonstrated that polypeptides could be synthesized from synthetic mRNA. They added an mRNA template to a number of tubes, each containing different radiolabeled amino acids, and measured radiation from the precipitated protein. This experiment was critical for understanding the relationship between the nucleotide sequence of mRNA and the amino acid sequence of the polypeptide it encodes.

Question 6

A protein called actin consists of 376 amino acids. The mRNA for actin must be longer than

Accepted Answer

A codon is a sequence of three nucleotides in mRNA that codes for a specific amino acid. There are 20 different amino acids commonly found in proteins, and therefore at least 20 different types of codons in mRNA. Since actin is composed of 376 amino acids, the mRNA sequence for actin must be at least 3 times longer, or 1128 nucleotides (3 x 376).

Question 7

You perform a cell free translation experiment like Nirenberg and Matthaei,but you forget to write down what nucleotides you added to make the mRNA.You precipitate the translated polypeptides and measure the relative amount of radiolabeled amino acids incorporated into them. You get 25% proline,25% threonine,12.5% glutamine,12.5% lysine,12.5% asparagine,and 12.5% histidine. What nucleotides and in what % did you add to make the mRNA?

Accepted Answer

The answer of 
You perform a cell free translation experiment...

Question 8

You are studying the DNA of a person who you know has two defective copies of the gene that encodes phenylalanine hydroxylase. You are surprised to find that this person also carries two defective copies of the gene for homogentisic acid oxidase. What disease symptoms will this person exhibit? (Assume pathway intermediates are not available from sources outside the phenylalanine breakdown pathway.)

Accepted Answer

The answer of 
 You are studying the DNA of a...

Question 9

Suppose you performed a triplet binding assay with the triplet 5′-UAA-3′.What radiolabeled amino acids do you expect to find bound to the filter?

Accepted Answer

The triplet 5′-UAA-3′ is a stop codon and therefore does not code for any amino acid. As a result, no radiolabeled amino acids are expected to be bound to the filter in this assay.

Question 10

Mutations in the enzyme homogentisic acid oxidase are associated with alkaptonuria.Select all characteristics of homogentisic acid oxidase.

Accepted Answer

Homogentisic acid oxidase is an enzyme, so it is encoded by a structural gene and has a primary, secondary, and tertiary structure with both an amino-terminal and carboxyl-terminal end. Also, it catalyzes a reaction in a metabolic pathway. It does not assist other polypeptides with folding into the correct secondary structure, so option E is incorrect.

Question 11

A tRNA's anticodon is 5′GGC3′.What amino acid is attached to it?

Accepted Answer

The answer of 
 A tRNA's anticodon is 5′GGC3′.What amino acid...

Question 12

Match between columns
                        Premises: Polypeptide released
Polypeptide grows
Ribosome and mRNA assemble

Accepted Answer

The Answer of Termination and Elongation and Initiation is...

Quiz 15: Translation of MRNA

What is the minimal number of tRNAs that can be used to recognize all of the codons for threonine?

You perform a cell free translation experiment like Nirenberg and Matthaei.You start with 60% C and 40% A.What relative amount of radiolabeled proline do you expect in the translated polypeptides?

The scientist(s) ________ developed a novel method to synthesize RNA.Short RNAs of 2 to 4 nucleotides were linked together to create a copolymer.The resulting peptide created after translation revealed the 3-letter code for the amino acids.

A protein called actin consists of 376 amino acids. The mRNA for actin must be longer than

Suppose you performed a triplet binding assay with the triplet 5′-UAA-3′.What radiolabeled amino acids do you expect to find bound to the filter?

Mutations in the enzyme homogentisic acid oxidase are associated with alkaptonuria.Select all characteristics of homogentisic acid oxidase.

A tRNA's anticodon is 5′GGC3′.What amino acid is attached to it?

Match each stage of translation to its best short description.