Exam 14: Translation and Proteins

During translation, which triplets signal chain termination?

A short segment of an mRNA molecule is shown below. The polypeptide it codes for is also shown: 5′-AUGGUGCUGAAG-3′: methionine-valine-leucine-lysine Assume that a mutation in the DNA occurs so that the fourth base (counting from the 5′ end) of the messenger RNA now reads A rather than G. What sequence of amino acids will the mRNA now code for? (You do not need a copy of the genetic code to answer the question.)

The term peptidyl transferase relates to ________.

The accompanying drawing represents simultaneous transcription and translation in E. coli. The direction of the RNA polymerase is given by the arrow. (a) Is the letter A nearer the 5′ or the 3′ end of the molecule? (b) Is the letter B nearer the 5′ or the 3′' end of the molecule? (c) Is the letter C nearer the 5′ or the 3′' end of the tRNA molecule? (d) What is the "S" value for the large rRNA that is closest to the letter D? (e) Which terminus (N or C) of the growing polypeptide chain is nearer to the letter E?

Much has been learned about the relationship between genes and gene products through the use of the mold Neurospora. What specific attributes make Neurospora a good organism for such studies?

Assuming that an amino acid sequence is 250 amino acids long, how many different molecules, each with a unique sequence, could be formed?

Given the accompanying table: 1 2 3 4 StrainA + - + - StrainB + + + - StrainC + + + + StrainD - - + - Where numbers 1 through 4 indicate four supplements that must be added to sustain growth of the organism. Determine a possible metabolic pathway that would give the results seen for the four mutant strains, A through D.

Exon shuffling is a term used to describe the movement of modular protein domains during protein evolution. As a result different genes specify similar domains.

What are polyribosomes?

Prokaryotic and eukaryotic ribosomes are structurally and chemically identical.

List at least three posttranslational modifications known to occur as a newly synthesized protein matures.

Sickle-cell anemia is caused by the absence of the alpha chain of hemoglobin.

Which of the following are among the major components of prokaryotic ribosomes?

Different domains in proteins impart different functional capabilities.

By their experimentation using the Neurospora fungus, Beadle and Tatum were able to propose the far-reaching hypothesis that ________.

The secondary structure of a protein includes ________.

Early in the 1900s, Sir Archibald Garrod studied a number of metabolic defects in humans. One particular disorder involved the inability to metabolize homogentisic acid. What is the name of this disorder?

Side groups of amino acids are typically classified under which of the following?

The accompanying table is a set of experimental results relating the growth (+) of Neurospora on several media (MM = minimal medium). Based on the information provided, present the biochemical pathway and the locations of the metabolic blocks.

Strain		Medium
	MM	MM+A	MM+B
s111	-	+	+
t60	+	+	+
s211	-	-	+

Draw and label the spatial and polarity relationships among the following translational components: ribosome (small and large subunits), growing polypeptide chains, amino acid attachment to tRNA, mRNA, codon, and anticodon.