CHEM214 Final Exam Spring 2022

T or F: The number of chromosomes and genes correlates strongly with the complexity of an organism.

FALSE. Neither one has a strong correlation.

T or F: A major component of RNA but not DNA is thymine.

FALSE. A major component of RNA but not DNA is uracil.

T or F: In the Watson-Crick model for the DNA double helix, there are two equally sized grooves that run up the sides of the helix.

FALSE. There are major and minor grooves.

T or F: The ratio of A+T/G+C is constant for all natural DNAs.

FALSE. A+G=T+C

T or F: In the Watson-Crick model of DNA structure: both strands run in the same direction, 5' to 3' they are parallel.

FALSE. They run in opposite directions and are anti-parallel.

T or F: In a mammalian cell, DNA repair systems: normally repair more than 99% of the DNA lesions that occur.

TRUE.

T or F: In base excision repair, only the first enzyme to act is: Dam methylase.

FALSE. DNA glycosylase.

T or F: DnaA is binding on oriC during initiation of DNA replication in E. coli.

TRUE.

T or F: In contrast to bacteria, eukaryotic chromosomes need multiple DNA replication origins because: eukaryotic chromosomes cannot usually replicate bidirectional.

FALSE. Their replication rate is much slower and it would take too long with only a single origin per chromosome.

T or F: The proofreading function of DNA polymerase involve: a 3'-5' exonuclease activity.

TRUE.

T or F: E. coli DNA polymerase III: can initiate without a primer.

False. It always requires a primer.

T or F: The DNA in a bacterial (prokaryotic) chromosome is BEST described as: a single circular double-helical molecule.

TRUE.

T or F: Introns: encode unusual amino acids in proteins.

FALSE. Extrons code not introns.

T or F: Approximately 1.5% of the human genome is transposal (Transposon) elements.

FALSE. about 45% is transposal.

B-form DNA in vivo is a ________-handed helix, _____ Å in diameter, with a rise of ____ Å per base pair.

Right, 20, 3.4

DNA replication in E. coli begins at a site in the DNA called the______.

origin

At the replication fork the_________ strand is synthesized continuously while the _________ is synthesized discontinuously.

leading, lagging

On the strand synthesized discontinuously, the short pieced are called _______ fragments.

Okazaki

An RNA primer for each of the fragments. is synthesized by an enzyme called ________, and this RNA primer is removed after the fragment is synthesized by the enzyme ________, using its _______ activity.

primase, DNA Pol I, 5'-> 3' exonuclease

The nicks. left behind in this. process are sealed by the enzyme ________.

DNA ligase

Based on Chargaff's rule, which base compositions for double-stranded DNA are possible?

%A%G %C %T %U

A) 5 45 45 5 0

B) 20 20 20 20 20

C) 35 15 35 15 0

D) All of the answers are correct.

E) None of the answers is correct.

A) 5 45 45 5 0

In the Watson-Crick model for the DNA double helix, which statement is NOT true?

A) The two strands run anti-parallel to one another.

B) The base-pairing occurs on the inside of the double helix.

C) The double helix is right-handed.

D) There are two equally sized grooves that run up the sides of the helix.

E) The two strands have complementary sequences.

D) There are two equally sized grooves that run up the sides of the helix.

When double-stranded DNA is heated at neutral pH, which change does not occur?

A) The absorption of ultraviolet (260 nm) light increases.

B) The covalent N-glycosidic bond between the base and the pentose breaks.

C) The helical structure unwinds.

D) The hydrogen bonds between A and T break.

E) The viscosity of the solution decreases.

B)The covalent N-glycosidic bond between the base and the pentose breaks.

Which DNA primer would have the HIGHEST melting temperature?

A) GCATCGGC

B) AATCGGAT

C) ATACAGATCGGC

D) ACCGGCAGGTCGGC

E) ATACGCAGATCGGC

D) ACCGGCAGGTCGGC

Which type of damage to DNA structure is MOST likely to be caused by UV light?

A) deamination

B) pyrimidine dimers

C) depurination

D) depyrimidination

E) hydrolysis of the phosphodiester bond

B) pyrimidine dimers

What type of bond links base to pentose in nucleotide?

N-glycosidic

What type of bond joins adjacent nucleotides in one strand?

phosphodiester

What type of bond joins complementary nucleotides in two strands?

hydrogen

What type of bond is the difference between a nucleoside and a nucleotide?

phosphate ester

Describe the composition and structure of a nucleosome.

A nucleosome consists of 146 base pairs of double-stranded DNA wrapped in a solenoidal supercoil around a core of histones (small, basic proteins). This core contains two copies of each histones H2A, H2B, H3, and H4.

Which deoxyoligonucleotide will hybridize with a DNA containing the sequence (5')AGACTGGTC(3')?

(5')GACCAGTCT(3')

T or F: RNA polymerase can synthesize RNA chains without a primer.

TRUE.

T or F: RNA polymerase from E. coli (core enzyme alone) can recognize specific start. signals in DNA.

FALSE. It recognizes the promoter.

T or F: The sigma factor of E. coli RNA polymerase: combines with the core enzyme to confer specific binding to a primer.

FALSE. It binds to a promoter.

T or F: Termination of transcription is a known factor of TFIIH

FALSE. DNA helicase activity, Hydrolysis of ATP, Formation of an open complex, Nucleotide excision repair

T or F: Processing of a primary mRNA transcript in a eukaryotic cell normally involve: conversion of normal bases to modified bases, such as inosine and pseudouridine.

FALSE: 5' cap, 3' polyA tail, and splice out intron.

T or F: The 5'-terminal cap structure of eukaryotic mRNAs is a(n): 7-methylguanosine joined to the mRNA via a 5' to 5' triphosphate linkage.

TRUE.

T or F: Compared with DNA polymerase, reverse transcriptase: makes more errors because it lacks the 3' to 5' proofreading exonuclease activity.

TRUE.

T or F: Telomerase consists of RNA only.

FALSE. RNA and protein.

T or F. Several different codons may encode. the. same amino acid.

TRUE.

T or F: The large subunit of Ribosome contains rRNA molecules: the small subunit does not.

FALSE. Both have rRNA.

T or F: Aminoacyl-tRNA synthetases (amino acid activating enzymes): "recognize" specifiC tRNA molecules and specific amino acids.

TRUE.

T or F: Aminoacyl-tRNA synthetases (amino acid activating enzymes): "recognize" any tRNA molecules and specific amino acids.

FALSE. Specific tRNA and specific amino acids.

T or F: Since introns are largely genetic 'junk', they do not have to be removed precisely from the primary transcript during RNA splicing.

FALSE. They must, otherwise you will get the wrong coding sequence.

T or F: All cells use one type of RNA polymerase to transcribe all classes of RNA.

FALSE. Eukaryotic cells have three types.

T or F: The large and small subunits of ribosomes undergo association and dissociation during each cycle of translation.

TRUE.

The formation of a peptide bond between two amino acids is an example of a(n) _________ reaction.

A) cleavage

B) condensation

C) group transfer

D) isomerization

E) oxidation reduction

B) condensation

Which of the following are features of the wobble hypothesis?

A) A naturally occurring tRNA exists in yeast that can read both arginine and lysine codons.

B) A tRNA can recognize only one codon.

C) Some tRNAs can recognize codons that specify two different amino acids if both are nonpolar.

D) The "wobble" occurs only in the first base of the anticodon.

E) The "wobble" occurs only in the third base of the anticodon.

D) The 'wobble' occurs only in the first base of the anticodon.

At the isoelectric pH of a tetrapeptide:

A) only the amino and carboxyl termini contribute charge.

B) the amino and carboxyl termini are not charged.

C) the total net charge is zero.

D) there are four ionic charges.

E) two internal amino acids of the tetrapeptide cannot have ionizable R groups.

C) the total net charge is zero

In a conjugated protein, a prosthetic group is:

A) a fibrous region of a globular protein.

B) a nonidentical subunit of a protein with many identical subunits.

C) a part of the protein that is not composed of amino acids.

D) a subunit of an oligomeric protein.

E) synonymous with "protomer."

C) A part of the protein that is not. composed of amino acids

Which of the following is not part of the miRNA formation?

A) Pri-miRNA

B) Pre-miRNA

C) Dicer

D) RISC

E) Pseudouridine

E) Pseudouridine

It is possible to convert the Cys that is a part of Cys-tRNACys to Ala by a catalytic reduction. If the resulting Ala-tRNACys were added to a mixture of (1) ribosomes, (2) all the other tRNAs and amino acids, (3) all of the cofactors and enzymes needed to make protein in vitro, and (4) mRNA for hemoglobin, where in the newly synthesized hemoglobin would the Ala from Ala-tRNACys be incorporated?

A) Nowhere; this is the equivalent of a nonsense mutation.

B) Wherever Ala normally occurs

C) Wherever Cys normally occurs

D) Wherever either Ala or Cys normally occurs

E) Wherever the dipeptide Ala-Cys normally occurs

C) Wherever Cys normally occurs

Which of the following best represents the backbone arrangement of two peptide. bonds?

A) C—N—C—C—C—N—C-C

B) C—N—C—C—N—C

C) C—N—C—C—C—N

D) C—C—N—C—C—N

E) C—C—C—N—C—C—C

D)C—C—N—C—C—N

Which one of the following statements about the elongation phase of protein synthesis is true?

A) At least five high-energy phosphoryl groups are expended for each peptide bond formed.

B) During elongation, incoming aminoacylated tRNAs are first bound in the P site.

C) Elongation factor EF-Tu facilitates translocation.

D) Peptidyl transferase catalyzes the attack of the carboxyl group of the incoming amino acid on an ester linkage in the nascent polypeptide.

E) Peptidal transferase is a ribozyme.

E) Peptidal transferase is a ribozyme.

T or F: Eukaryotic cells have three distinct RNA polymerases.

TRUE

T or F: Eukaryotic cells mRNAs are generally synthesized by RNA polymerase I.

FALSE

T or F: Eukaryotic cells RNA polymerase III synthesizes only rRNAs.

FALSE

T or F: Eukaryotic cells 5S rRNA is synthesized by RNA polymerase I.

FALSE

T or F: Eukaryotic cell's RNA polymerases initiate transcription at specific promoter sites on the DNA.

TRUE

Function of mRNA

codes for proteins

Function of rRNA

components of ribosomes

Function of snRNA

splicing of RNA transcripts

Function of tRNA

adaptor for protein synthesis