Bio218 - Exam 2

In the partial diploid pair: I-P+OcZ-Y+ / IsP+O+Z+Y+ Which of the following represents what would happen for the production of β-gal and Permease before and after the addition of lactose?

- + / - +

Which of the following is a difference in the process of initiation of translation between prokaryotes and eukaryotes? 1. The amino group of the methionine on the initiator tRNA is not formylated in eukaryotes as it is in prokaryotes. 2. The initiation complex forms at the 5' terminus of the mRNA, not at the Shine-Dalgarno/AUG translation start site as in prokaryotes. 3. The process takes place at the ribosome in prokaryotes but not in eukaryotes.

1 and 2

Which factor is responsible for delivery of the charged tRNA to the A site of the ribosome?

EF-Tu

The lac [x] gene encodes the lac repressor. When lactose is absent, this repressor is bound to the [y], but when lactose is present, the repressor binds [z] instead.

I, operator (RPBS), allolactose

Which of the following would be a constitutive mutation(s)? a. I- b. P- c. Oc d. I+ e. I-d f. Is

I-, Oc, I-d

During initiation of translation in E. coli, which factor binds GTP and facilitates the combining of complex #1 and #2 to make the initiation complex prior to the addition of the 50S subunit?

IF-1

During eukaryotic initiation of translation, methionyl-tRNAiMet interacts with soluble initiation factors and binds at the ribosomal __________ site.

P

Diptheria toxin is lethal by inhibiting protein synthesis in cells of the upper respiratory tract of infected persons. The target of the Diptheria toxin is EF-2 (which is the counterpart to prokaryote's EF-G). Why is it so lethal? a. EF-2 is needed for moving tRNA from the A-site to the P-site of the ribosome during protein translational translocation. b. Ef-2 inhibits the release of the nascent polypeptide from the P-site so that the functional protein is never produced. c. EF-2 inhibits the transfer of the tRNA with the growing polypeptide chain from the P-site to the E-site. d. Inhibiting EF-2 prevents the 60S ribosomal subunit from joining the initiation complex to form the complete ribosome. e. Inhibiting EF-2 prevents the hydrolysis of GTP so that tRNA's cannot be charged

a. EF-2 is needed for moving tRNA from the A-site to the P-site of the ribosome during protein translational translocation.

Which of the following states describes inducible expression? a. Resting state is off and free repressor binds the RPBS b. Resting state is off and repressor/co-repressor binds the RPBS c. Resting state is on and free repressor binds the RPBS d. Resting state is on and repressor/co-repressor binds the RPBS

a. Resting state is off and free repressor binds the RPBS

What is the activity of the following genotype? I+ Oc Z+ Y+ / I+ O+ Z+ Y+ a. constitutive b. inducible c. repressed

a. constitutive

For Translation, each tRNA must be loaded with the correct amino acid. This activity is carried by __________________ and requires ___________.

aminoacyl-tRNA synthetase; ATP

Which of the following genotypes will produce β-galactosidase and β-galactoside permease if lactose is absent? (a). I+ O+ Z+ Y+ (b). I- Oc Z+ Y+ (c). Is Oc Z+ Y+ (d). Is O+ Z+ Y+ (e). I- O+ Z + Y+

b, c, e

Which of the following statements is correct about RNA involvement in translation? a. Only eukaryotic precursor rRNA is processed into smaller functional units via cleavage by endoribonucleases. b. Aminoacyl-tRNA synthetases are responsible for attaching amino acids to the appropriate tRNAs. c. The nucleolus is responsible for the synthesis of tRNAs catalyzed by RNA Pol II. d. rRNA genes get translated into ribosomal proteins in the cytoplsm. e. The adapter molecule of protein synthesis are rRNA that recognize the anticodons of the mRNA molecule to direct protein synthesis.

b. Aminoacyl-tRNA synthetases are responsible for attaching amino acids to the appropriate tRNAs.

Which of the following statements is NOT true about protein tertiary structure. a. All proteins display tertiary structure. b. Only proteins with disulfide bridges can achieve tertiary structure. c. Tertiary structure is influenced by interaction between molecules and the environment (solvent) the protein is in. d. Most polypeptides will fold spontaneously into their final most energetically stable conformation. e. Some proteins require chaperones to achieve their tertiary structure.

b. Only proteins with disulfide bridges can achieve tertiary structure.

Which of the following statements is NOT true about eukaryotic initiation? a. 7-MG cap on 5' end of mRNA bound is bound by cap binding protein (CBP) b. Other initiation factors bind CBP followed by the 30S subunit c. Methionyl-tRNAiMet interacts with soluble initiation factors and binds the ribosomal P site d. Complex moves 5' to 3' on mRNA searching for start codon (AUG) e. Once at start codon, initiation factors fall off and 60S subunit binds to complete the complex

b. Other initiation factors bind CBP followed by the 30S subunit (its the 40S!)

When an activator binds to the operator in the absence of the co-repressor, but not in it's presence, this is known as: a. Positive regulation of an inducible system b. Positive regulation of a repressible system c. Negative regulation of an inducible system d. Negative regulation of a repressible system

b. Positive regulation of a repressible system

Given the following genotype, how would the activity of the lac operon change if glucose was added to media already containing lactose?I- P+ O+ Z+ Y- a. There would be no change because there is no LacI repressor. b. The activity of the lac operon would decrease due to catabolite repression. c. The activity of the lac operon would increase due to catabolite repression. d. There would be no change because B-galactosidase and the permease cannot be made by this genotype.

b. The activity of the lac operon would decrease due to catabolite repression.

In posttranslational control, protein degradation is determined by regions rich in one of four amino acids. Which of the following is NOT associated with protein degradation in less than 2 hours? a. Proline b. Tryptophan c. Serine d. Glutamic acid e. Threonine

b. Tryptophan

Which of the following statements about translational or post-translational control is NOT true? a. Feedback inhibition occurs at the level of enzymatic activity when endproducs bind at the effector molecule binding site. b. Variations in the Shine-Dalgarno sequence can lead to different rates of translation. c. Proteins that are rich in Proline, Glycine, Serine and Threonine tend to be degraded quickly in less than 2 hours. d. In polycistronic mRNA, genes located furthest from the promoter are translated less efficiently than those closet to the promoter. e. Modifications of the N-terminal amino acid of certain enzymes can alter the half life of that enzyme.

c. Proteins that are rich in Proline, Glycine, Serine and Threonine tend to be degraded quickly in less than 2 hours.

Which of the following statements is NOT true when a bacterial cell is in an environment where tryptophan is lacking? a. The ribosome stalls at the two Trp codons in the leader sequence. b. Transcription proceeds through the entire trp operon. c. Region 3 is paired with region 4 to form the transcription termination hairpin. d. There are low levels of Trp-tRNAtrp in the cell. e. Translation will proceed so that Tryptophan is made.

c. Region 3 is paired with region 4 to form the transcription termination hairpin.

What is positive gene regulation? a. When an effector protein binds to DNA to change gene expression b. When an activator protein binds to the operator of a gene to turn expression off c. When an activator protein binds to the operator of a gene to turn expression on d. When a repressor protein binds to the operator of a gene to turn expression on e. When a repressor protein binds to the operator of a gene to turn expression off

c. When an activator protein binds to the operator of a gene to turn expression on

Which type of regulation best describes when an inactive activator/co-repressor complex cannot bind to the RPBS thus preventing transcription? a. negative control of a repressible system b. positive control of an inducible system c. positive control of a repressible system d. Attenuation of transcription e. negative control of an inducible system

c. positive control of a repressible system

In a negative, inducible regulatory mechanism, transcription of the structural gene(s) occurs in a. the presence of the co-repressor, but not in its absence. b. the absence of the inducer, but not in its presence. c. the presence of the inducer, but not in its absence. d. the absence of the co-repressor, but not in its presence. e. the absence or presence of the effector molecule.

c. the presence of the inducer, but not in its absence.

Proteins that help nascent polypeptides form the correct three dimensional structure are known as:

chaperone proteins

In the following mutant, would lac operon expression be constitutive, inducible or repessed? IsP+OcZ+Y+

constitutive

In prokaryotes, the peptidyl transferase activity needed to carryout our elongation during translation is supplied by ______________ a. 30S subunit b. EF-Tu c. EF-G d. 50S subunit e. 40S subunit

d. 50S subunit

What enzymes are responsible for charging tRNA with the specific amino acid prior to translation? a. Peptidyl transferase b. tRNA chargase c. Peptidyl synthetase d. Amino-acyl tRNA synthetase e. Amino-acyl tRNA transferase

d. Amino-acyl tRNA synthetase

According to the N-end Rule, which modification of the N terminal amino acid would produce a beta-galactosidase enzyme with a very short half-life? a. Ser b. Ala c. Val d. Arg e. Met

d. Arg

According to the "wobble" hypothesis inosine on tRNA can base pair with all the following ribonucleotides in the mRNA EXCEPT _____________ in the 3rd position. a. Uracil b. Adenine c. Cytosine d. Guanine

d. Guanine

Which genotype will have B-gal enzymatic activity in the presence of lactose but not in its absence? a. I- P+ Oc Z+ Y+/ I+ P+ O+ Z- Y+ b. I+ P+ Oc Z+ Y-/ Is P+ O+ Z- Y+ c. I+ P- O+ Z+ Y-/ I- P+ Oc Z- Y+ d. I- P+ O+ Z+ Y+/ I+ P+ O+ Z+ Y- e. I+ P- O+ Z+ Y+/ I+ P+ O+ Z- Y+

d. I- P+ O+ Z+ Y+/ I+ P+ O+ Z+ Y-

Which of the following statements is true about eukaryotic initiation of translation? a. There is a formyl group on the initiation methionine b. Initiation complex forms at the Shine-Dalgarno/AUG translation start site c. After binding at the 3' poly-A tail, the ribosome scans the mRNA and begins translation at the first available AUG d. The initiator methionyl-tRNA interacts with a soluble initiation factor and enters the P-site directly e. All of these statements are true.

d. The initiator methionyl-tRNA interacts with a soluble initiation factor and enters the P-site directly

Which level of regulation has the largest effect on phenotype? a. Translation b. RNA stability c. Post-translation d. Transcription e. RNA processing

d. Transcription

Which of the following statements about protein structure is correct? a. The primary structure of a protein does not dictate the final shape of the protein. b. Ionic bonds in tertiary structure maintain a strong attraction between amino acids in the interior of living cells. c. Tertiary protein structure is maintained primarily by covalent disulfide bridges. d. Two common types of secondary structure are α helices and β sheets, both of which are held in place via hydrogen bonds. e. All peptides exhibit four levels of structural organization: primary, secondary, tertiary, and quaternary.

d. Two common types of secondary structure are α helices and β sheets, both of which are held in place via hydrogen bonds.

All of the amino acids, except proline, contain: a. A free amine group b. A free carboxyl group and a free R group c. A free R group d. A free carboxyl group e. A free amine group and a free carboxyl group

e. A free amine group and a free carboxyl group; Proline is one of the "special" amino acids that has a ring structure that involves the amino group. Proline introduces bends and kinks in the polypeptide chain.

Which of the following is an example of the degeneracy of the genetic code? a. The start codon is always AUG b. The genetic code is not degenerate c. Each codon specifies more than one amino acid d. The first two bases specify the amino acid e. A given amino acid has more than one codon

e. A given amino acid has more than one codon (degenerate meaning redundant!)

The target of the Diptheria Toxin is EF-2 which is the counterpart to EF-G in prokaryotes. What is the function of EF-2? a. Inhibits peptidyl transferase activity. b. Blocks the exit of the tRNA from the E-site. c. Inhibits the formation of the complete ribosome. d. Inhibits the delivery of the charged tRNA to the A site. e. Inhibits the movement of tRNA from the A-site to the P-site.

e. Inhibits the movement of tRNA from the A-site to the P-site.

Activity of the Trp operon is turned down in two ways: repression and attentuation. Attenuation is best described as: a. Post-translational regulation b. Catabolite repression c. Negative control of a repressible system d. Positive control of a repressible system e. Translation regulating transcription

e. Translation regulating transcription

In the regulation of the trp operon by attenuation, which of the following structures formed by the trpL mRNA will ALLOW transcription to occur? a. When region 1 base pairs with region 2 and region 3 with region 4 b. When region 2 base pairs with region 4, allowing transcription to proceed past the attenuation sequence c. When none of the regions are base paired so that there are no hairpin structures to prevent transcription d. When region 1 base pairs with region 3, leaving region 4 available for transcription e. When region 2 base pairs with region 3, preventing region 3 from base pairing with region 4

e. When region 2 base pairs with region 3, preventing region 3 from base pairing with region 4

In a positive, repressible regulatory mechanism, transcription of the structural gene(s) occurs in a. the presence of the co-repressor, but not in its absence b. the absence or presence of the co-repressor c. the presence of the inducer, but not in its absence d. the absence of the inducer, but not in its presence e. the absence of the co-repressor, but not in its presence

e. the absence of the co-repressor, but not in its presence

The general term for molecules that influence the DNA binding behavior of a regulatory protein are called? Specific examples include allolactose and tryptophan.

effector

During initiation in prokaryotes, the Shine-Dalgarno sequence binds to a. 5S rRNA in the 30S subunit b. 28S rRNA in the 60S subunit c. 5S rRNA in the 40S subunit d. 23S rRNA in the 50S subunit e. 18S rRNA in the 40S subunit f. 16S rRNA in the 30S subunit

f. 16S rRNA in the 30S subunit

T/F: Attenuation of the Trp operon occurs due to stalling of the ribosome at two Trp codons on the leader peptide, which is part of the Trp operon.

false

T/F: In the lysine riboswitch, when NO lysine is present in the environment, the expression domain forms a hairpin with the antiterminator to inhibit trasncription.

false; In the lysine riboswitch, when NO lysine is present in the environment, the expression domain forms a hairpin with the antiterminator ALLOWING transcription to occur.

T/F: During termination of translation, when STOP codon appears at the A site, Release Factors (RFs) enter and alter the carboxyl transferase activity and H2O is added to the COOH terminus releasing the peptide chain.

false; RF enter and alter PEPTIDYL transferase activity

T/F: When charging a tRNA with its appropriate amino acid, the bond is formed between the 3' OH terminus of the tRNA and the free amino group of the amino acid.

false; its the free CARBOXYL group, not amino

In the situation where cAMP is low so that CAP is not bound to the promoter and allolactose is bound to the repressor removing it from the operator, what would be the expected levels of glucose and lactose?

high glucose; high lactose

What type of bonding is responsible for the formation of alpha helices and beta sheets?

hydrogen bonds

In a cytosolic globular protein, ________ amino acids would be found on the outside of the folded protein, while _________ amino acids would be found in the interior.

hydrophilic/polar; hydrophobic/nonpolar

Which gene of the lac operon codes for the repressor protein?

lac I

During catabolite repression, which scenario will result in expression of the structural genes of the lac operon?

low glucose, high lactose

The catabolite repression of the lac operon is mediated by catabolite activator protein and cyclic AMP. When glucose is high, cyclic AMP is ________ and CAP protein is _________.

low; not bound to the promoter

The Trp Operon is an example of a [a] repressible system, where [b] is co-repressor that when added lowers the rate of transcription [c].

negative; Trp; 70x

In eukaryotes, rRNA is synthesized in the ________ by _________.

nucleolus; RNA pol I

For the following phenotype which products will be produced in the presence of lactose? I-dP+O+Z+Y- / I+P-O+Z-Y+

only lac Z (B-galactosidase)

Based on its side chain, how would the following amino acid be classified? CH2 -- CH2 -- C = O, --N2H

polar (free, uncharged oxygen)

Which amino acid introduces bends and kinks in a peptides secondary structure?

proline

The association of two or more polypeptides in a multimeric protein is known as the:

quaternary structure

In a cytosolic protein, where would you expect the a polar amino acid to be found?

to the outside of the protein (hydrophilic)

_____________________ regulation has the largest effect on phenotype

transcriptional

cells devote more energy to ___________ than any other process

translation

T/F: Attenuation works in bacteria because transcription and translation is con-current in prokaryotes.

true

T/F: In Negative Autogenous Regulation, in the absence of rRNA, L4 is able to bind to the 5' end of the S10 mRNA, preventing further ribosome binding and therefore further translation of the mRNA.

true

T/F: In the Lysine Riboswitch, when the expression domain forms a hairpin with the antiterminator, the Lys structural genes are transcribed.

true