Deck 14: The Genetic Code and Translation

Question 1

Beadle and Tatum's studies of biochemical pathways in the fungus Neurospora helped define the relation between genotype and phenotype by establishing the one gene, one enzyme hypothesis, the idea that each gene encodes a separate enzyme. This hypothesis was later modified to the one gene, one polypeptide hypothesis.

-Auxotrophic mutation 103 grows on minimal medium supplemented with A, B, or C; mutation 106 grows on medium supplemented with A and C but not B; and mutation 102 grows only on medium supplemented with C. What is the order of A, B, and C in a biochemical pathway?

Answer 1

B $\rightarrow$ A $\rightarrow$ C

Question 2

The products of many genes are proteins whose actions produce the traits encoded by these genes. Proteins are polymers consisting of amino acids linked by peptide bonds. The amino acid sequence of a protein is its primary structure. This structure folds to create the secondary and tertiary structures; two or more polypeptide chains may associate to create a quaternary structure.
-What primarily determines the secondary and tertiary structures of a protein?

Answer 2

The amino acid sequence (primary structure) of the protein

Question 3

The genetic code is a triplet code, in which three nucleotides encode each amino acid in a protein.

-A codon is

A) one of three nucleotides that encode an amino acid.
B) three nucleotides that encode an amino acid.
C) three amino acids that encode a nucleotide.
D) one of four bases in DNA

Answer 3

three nucleotides that encode an amino acid.

Question 4

The genetic code consists of 61 sense codons that specify the 20 common amino acids; the code is degenerate, meaning that some amino acids are encoded by more than one codon. Isoaccepting tRNAs are different tRNAs with different anticodons that specify the same amino acid. Wobble exists when more than one codon can pair with the same anticodon.

-Through wobble, a single ____________________ can pair with more than one ____________________.

A) codon, anticodon
B) group of three nucleotides in DNA, codon in mRNA
C) tRNA, amino acid
D) anticodon, codon

Question 5

Each sequence of nucleotides possesses three potential reading frames. The correct reading frame is set by the initiation codon. The end of a protein-encoding sequence is marked by a termination codon. With a few exceptions, all organisms use the same genetic code.
-Do the initiation and termination codons specify an amino acid? If so, which ones?

Question 6

Amino acids are attached to specific tRNAs by aminoacyl-tRNA synthetases in a two-step reaction that requires ATP.

-Amino acids bind to which part of the tRNA?

A) anticodon
B) DHU arm
C) 3' end
D) 5' end

Question 7

In the initiation of translation in bacterial cells, the small ribosomal subunit attaches to mRNA, and initiator tRNA attaches to the initiation codon. This process requires several initiation factors (IF-1, IF-2, and IF-3) and GTP. In the final step, the large ribosomal subunit joins the initiation complex.
-During the initiation of translation, the small ribosome binds to which consensus sequence in bacteria?

Question 8

Elongation consists of three steps: (1) a charged tRNA enters the A site, (2) a peptide bond is created between amino acids in the A and P sites, and (3) the ribosome translocates to the next codon. Elongation requires several elongation factors and GTP.

-In elongation, the creation of peptide bonds between amino acids is catalyzed by

A) rRNA.
B) protein in the small subunit.
C) protein in the large subunit.
D) tRNA.

Question 9

In both prokaryotic and eukaryotic cells, multiple ribosomes may be attached to a single mRNA, generating a structure called a polyribosome.

-In a polyribosome, the polypeptides associated with which ribosomes will be the longest?

A) Those at the 5' end of mRNA
B) Those at the 3' end of mRNA
C) Those in the middle of mRNA
D) All polypeptides will be the same length.