Deck 14: Translation and Proteins

Question 1

Knowing that the base sequence of any given messenger RNA is responsible for precisely ordering the amino acids in a respective protein,present two mechanisms by which intrinsic properties of mRNA may regulate the "net output" of a given gene.

Answer 1

(a)Final output of a given gene may be influenced by the stability of an mRNA,and stability of an mRNA is determined in part by its base content and sequence.(b)Differential splicing of mRNA (actually mRNA precursors)can influence how much of a given product will be made from a gene.

Question 2

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.)

A) methionine-valine-leucine-lysine
B) methionine-lysine-leucine-lysine
C) methionine-leucine-leucine-lysine
D) methionine-valine-methionine-lysine
E) methionine-methionine-leucine-lysine

Answer 2

E

Question 3

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

A) polar, nonpolar
B) linear, circular
C) alpha, omega
D) long, short
E) primary, secondary

Answer 3

A

Question 4

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

A) prototrophs will grow only if provided with nutritional supplements
B) several different enzymes may be involved in the same step in a biochemical pathway
C) the role of a specific gene is to produce a specific enzyme
D) genetic recombination occurred in Neurospora
E) more than one codon can specify a given amino acid

Question 5

The secondary structure of a protein includes ________.

A) gamma and delta
B) alpha and gamma
C) α-helix and β-pleated sheet
D) hydrophobic clusters
E) disulfide bridges

Question 6

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.

Question 7

During translation,which triplets signal chain termination?

Question 8

Assume that a base addition occurs early in the coding region of a gene.Is the protein product of this gene expected to have more or fewer altered amino acids compared with the original gene with a base deletion late in the coding region?

Question 9

Describe each of the following parameters that relate to the structure and function of tRNA:
(a) four functional domains
(b) Wobble hypothesis

Question 10

Three major types of RNAs are mRNA,rRNA,and tRNA.For each of the conditions below,predict the consequences in terms of the population of proteins being synthesized in a particular cell.What qualitative and quantitative changes,if any,are expected in the individual protein involved (if one is involved)and in the population of proteins in this cell?
(a)An acridine dye-induced mutation (adds or deletes single bases in DNA)leads to an mRNA for one protein-producing gene.The condition is heterozygous in the involved cell.
(b)A deletion (homozygous)that removes approximately half of the rRNA genes.

Question 11

The β chain of adult hemoglobin is composed of 146 amino acids of a known sequence.In comparing the normal β chain with the β chain in sickle cell hemoglobin,what alteration is one likely to find?

A) valine instead of glutamic acid in the sixth position
B) glutamic acid replacing valine in the first position
C) extensive amino acid substitutions
D) trinucleotide repeats
E) frameshift substitutions

Question 12

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

A) 12S rRNA, 5.8S rRNA, and proteins
B) 16S rRNA, 5.8S rRNA, and 28S rRNA
C) 16S rRNA, 5S rRNA, and 23S rRNA
D) lipids and carbohydrates
E) 18S rRNA, 5.8S rRNA, and proteins

Question 13

A protein is 300 amino acids long.Which of the following could be the number of nucleotides in the section of DNA that codes for this protein? (Remember: DNA is double-stranded.)

A) 3
B) 100
C) 300
D) 500
E) 1800

Question 14

The primary structure of a protein is determined by ________.

A) the sequence of amino acids
B) hydrogen bonds formed between the components of the peptide linkage
C) a series of helical domains
D) pleated sheets
E) covalent bonds formed between fibroin residues

Question 15

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 orC)of the growing polypeptide chain is nearer to the letter E?

Question 16

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?

Question 17

The one-gene:one-enzyme hypothesis emerged from work on which two organisms?

A) E. coli and yeast
B) Drosophila and humans
C) Neurospora and Drosophila
D) E. coli and humans
E) All of the answers listed are correct.

Question 18

Which protein class directly controls many of the metabolic reactions within a cell?

A) structural proteins
B) repressor proteins
C) operator proteins
D) enzymes
E) hydrophilic proteins

Question 19

The term peptidyl transferase relates to ________.

A) base additions during mRNA synthesis
B) peptide bond formation during protein synthesis
C) elongation factors binding to the large ribosomal subunit
D) discontinuous strand replication
E) 5′ capping of mRNA

Question 20

What are polyribosomes?

Question 21

Regarding the protein structure,how are β-pleated sheets arranged and stabilized?

Question 22

In what ways do the amino acid side chains interact to influence protein function?

Question 23

Nutritional mutants in Neurospora can be "cured" by treating the medium with substances in the defective metabolic pathway.What determines whether the mutant strain (auxotroph)is "cured" by a particular substance?

Question 24

Given the accompanying table:
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.

Question 25

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.

Question 26

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

Question 27

Below are several phenomena relating to protein structure.Clearly describe each phenomenon,the conditions under which each occurs,and the probable influence each has on protein structure.
(a) hydrophobic interactions
(b) hydrogen bonds
(c) disulfide bridges

Question 28

The following table presents the effect of different media on the growth response of tryptophan mutations in Salmonella typhimurium (+ = growth,- = no growth).
(a) Construct the biochemical pathway for the compounds IGP,AA,IN,and TRY based on these data.
(b) Place strains of bacteria (mutations)in the appropriate steps in the pathway.
(c) In bacteria it is often possible to make partial diploid strains.Assume that a diploid strain was made containing the complete genomes of the trp-2 and trp-1 strains.Would this diploid strain be able to grow on the unsupplemented medium? Explain your answer.

Question 29

Which class of protein functions primarily by lowering the energy of activation during a reaction?

Question 30

What is the structure of fetal hemoglobin (HbF)?

Question 31

Describe the conceptual basis for constructing biochemical pathways using nutrient supplement experiments with Neurospora.

Question 32

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

Question 33

What is the general ethnic distribution of the sickle-cell gene?

Question 34

Electrophoretic separation of HbA from HbS is based on a difference in their ________.

Question 35

The problem below relates to the synthesis of several intermediates in the citric acid cycle,which is essential in the production of ATP through aerobic respiration.A set of experimental results relating the growth (+)of Neurospora on several media is given in the table.Based on the information provided,present the biochemical pathway for the substances oxaloacetate,fumarate,malate,and succinate,and the locations of the metabolic blocks produced by the various strains.

Question 36

Considering the types of side chains on amino acids and their relationship to protein structure,where are the amino acids with hydrophobic side chains most likely to be located?

Question 37

Describe the basic structure of normal adult hemoglobin and the abnormality observed in sickle-cell hemoglobin.

Question 38

A procedure that is often used to separate molecules by using their molecular charges is called ________.

Question 39

Studies of Neurospora led to the ________ statement,whereas studies of human hemoglobin led to the ________ statement.

Question 40

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?

Question 41

Prokaryotic and eukaryotic ribosomes are structurally and chemically identical.

Question 42

The primary structure of a protein is composed of the sequence of amino acids in that protein.

Question 43

Proteins are composed of strings of nucleotides connected together by 5′-3′ phosphodiester bonds.

Question 44

The ribonucleic acid components known to exist in eukaryotic ribosomes are the following: 5.8S,18S,28S,and 5S.

Question 45

rDNA is the portion of a genome that is involved in the production of ribosomal RNA.

Question 46

Different domains in proteins impart different functional capabilities.

Question 47

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

Question 48

The secondary structure of a protein is dependent on polar interactions among the side chains of the amino acids.

Question 49

When a metabolic block occurs in a biochemical pathway,it is common for amount of the substance immediately prior to that block to increase.

Question 50

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.