Bio Final

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? A) 8% B) 16% C) 31% D) 42% E) It cannot be determined from the information provided.

8%

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is A) 3' UCA 5'. B) 3' UGA 5'. C) 5' TCA 3'. D) 3' ACU 5'.

A) 3' UCA 5'

Which of the following is not true of RNA processing? A) Exons are cut out before mRNA leaves the nucleus. B) Nucleotides may be added at both ends of the RNA. C) Ribozymes may function in RNA splicing. D) RNA splicing can be catalyzed by spliceosomes. E) A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.

A) Exons are cut out before mRNA leaves the nucleus.

Which of the enzymes separates the DNA strands during replication? A) I B) II C) III D) IV E) V

A) I

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? A) an assembled ribosome with a polypeptide attached to the tRNA in the P site B) separated ribosomal subunits, a polypeptide, and free tRNA C) an assembled ribosome with a separated polypeptide D) separated ribosomal subunits with a polypeptide attached to the tRNA

A) an assembled ribosome with a polypeptide attached to the tRNA in the P site

The anticodon of a particular tRNA molecule is A) complementary to the corresponding mRNA codon. B) complementary to the corresponding triplet in rRNA. C) the part of tRNA that bonds to a specific amino acid. D) changeable, depending on the amino acid that attaches to the tRNA. E) catalytic, making the tRNA a ribozyme.

A) complementary to the corresponding mRNA codon.

Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication? A) double-stranded DNA, four kinds of dNTPs, primers, origins B) topoisomerases, telomerases, polymerases C) G-C rich regions, polymerases, chromosome nicks D) nucleosome loosening, four dNTPs, four rNTPs E) ligase, primers, nucleases

A) double-stranded DNA, four kinds of dNTPs, primers, origins

A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that A) many noncoding stretches of nucleotides are present in mRNA. B) there is redundancy and ambiguity in the genetic code. C) many nucleotides are needed to code for each amino acid. D) nucleotides break off and are lost during the transcription process. E) there are termination exons near the beginning of mRNA.

A) many noncoding stretches of nucleotides are present in mRNA.

The leading and the lagging strands differ in that A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction. B) the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end. C) the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.

A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

In an analysis of the nucleotide composition of DNA, which of the following will be found? A) A = C B) A = G and C = T C) A + C = G + T D) G + C = T + A

A+C = G+T

Which component is not directly involved in translation? A) mRNA B) DNA C) tRNA D) ribosomes E) GTP

B) DNA

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture? A) DNA polymerase B) DNA ligase C) nucleotides D) Okazaki fragments E) primase

B) DNA ligase

What is the function of the release factor (RF)? A) It separates tRNA in the A site from the growing polypeptide. B) It binds to the stop codon in the A site in place of a tRNA. C) It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond. D) It supplies a source of energy for termination of translation. E) It releases the ribosome from the ER to allow polypeptides into the cytosol.

B) It binds to the stop codon in the A site in place of a tRNA

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation? A) No proofreading will occur. B) No replication fork will be formed. C) The DNA will supercoil. D) Replication will occur via RNA polymerase alone. E) Replication will require a DNA template from another source.

B) No replication fork will be formed.

Which of the following statements best describes the termination of transcription in prokaryotes? A) RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase. B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript. C) RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript. D) Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. E) RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA.

B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

What is meant by the description "antiparallel" regarding the strands that make up DNA? A) The twisting nature of DNA creates nonparallel strands. B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. C) Base pairings create unequal spacing between the two DNA strands. D) One strand is positively charged and the other is negatively charged. E) One strand contains only purines and the other contains only pyrimidines

B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

Which of the following statements is true about protein synthesis in prokaryotes? A) Extensive RNA processing is required before prokaryotic transcripts can be translated. B) Translation can begin while transcription is still in progress. C) Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles. D) Translation requires antibiotic activity. E) Unlike eukaryotes, prokaryotes require no initiation or elongation factors.

B) Translation can begin while transcription is still in progress.

The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following? A) polypeptide factors plus ATP B) polypeptide factors plus GTP C) polymerases plus GTP D) SRP plus chaperones E) signal peptides plus release factor

B) polypeptide factors plus GTP

A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that A) none of the proteins in the cell will contain phenylalanine. B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. C) the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons. D) the ribosome will skip a codon every time a UUU is encountered. E) none of the options will occur; the cell will recognize the error and destroy the tRNA.

B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

An Okazaki fragment has which of the following arrangements? A) primase, polymerase, ligase B) 3' RNA nucleotides, DNA nucleotides 5' C) 5' RNA nucleotides, DNA nucleotides 3' D) DNA polymerase I, DNA polymerase III E) 5' DNA to 3'

C) 5' RNA nucleotides, DNA nucleotides 3'.

Which of the following does not occur in prokaryotic gene expression, but does in eukaryotic gene expression? A) mRNA, tRNA, and rRNA are transcribed. B) RNA polymerase binds to the promoter. C) A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end. D) Transcription can begin as soon as translation has begun even a little. E) RNA polymerase requires a primer to elongate the molecule.

C) A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.

The nitrogenous base adenine is found in all members of which group? A) proteins, triglycerides, and testosterone B) proteins, ATP, and DNA C) ATP, RNA, and DNA D) α glucose, ATP, and DNA E) proteins, carbohydrates, and ATP

C) ATP, RNA, and DNA

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction? A) primase B) DNA ligase C) DNA polymerase III D) topoisomerase E) helicase

C) DNA polymerase III

A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. Where does tRNA #2 move to after this bonding of lysine to the polypeptide? A) A site B) P site C) E site D) exit tunnel E) directly to the cytosol

C) E site

Which of the enzymes covalently connects segments of DNA? A) I B) II C) III D) IV E) V

C) III

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? A) It synthesizes RNA nucleotides to make a primer. B) It catalyzes the lengthening of telomeres. C) It joins Okazaki fragments together. D) It unwinds the parental double helix. E) It stabilizes the unwound parental DNA.

C) It joins Okazaki fragments together.

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? A) ligase B) RNA polymerase I C) RNA polymerase II D) RNA polymerase III E) primase

C) RNA polymerase II

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is A) TTT. B) UUA. C) UUU. D) AAA.

C) UUU.

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following? A) the evolution of telomerase enzyme B) DNA polymerase that cannot replicate the leading strand template to its 5' end C) gaps left at the 5' end of the lagging strand D) gaps left at the 3' end of the lagging strand because of the need for a primer E) the "no ends" of a circular chromosome

C) gaps left at the 5' end of the lagging strand

What is the function of DNA polymerase III? A) to unwind the DNA helix during replication B) to seal together the broken ends of DNA strands C) to add nucleotides to the 3' end of a growing DNA strand D) to degrade damaged DNA molecules E) to rejoin the two DNA strands (one new and one old) after replication

C) to add nucleotides to the 3' end of a growing DNA strand

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence? A) 5' G C C T A G G 3' B) 3' G C C T A G G 5' C) 5' A C G T T A G G 3' D) 5' A C G U U A G G 3' E) 5' G C C U A G G 3'

D) 5' A C G U U A G G 3'

Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments? A) I B) II C) III D) IV E) V

D) IV

Which of the following is not true of a codon? A) It consists of three nucleotides. B) It may code for the same amino acid as another codon. C) It never codes for more than one amino acid. D) It extends from one end of a tRNA molecule. E) It is the basic unit of the genetic code.

D) It extends from one end of a tRNA molecule.

Which of the following would you expect of a eukaryote lacking telomerase? A) a high probability of somatic cells becoming cancerous B) production of Okazaki fragments C) inability to repair thymine dimers D) a reduction in chromosome length after replication E) high sensitivity to sunlight

D) a reduction in chromosome length after replication

Which of the following nucleotide triplets best represents a codon? A) a triplet separated spatially from other triplets B) a triplet that has no corresponding amino acid C) a triplet at the opposite end of tRNA from the attachment site of the amino acid D) a triplet in the same reading frame as an upstream AUG E) a sequence in tRNA at the 3' end

D) a triplet in the same reading frame as an upstream AUG

The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method? A) adding a single 5' cap structure that resists degradation by nucleases B) causing specific double-strand DNA breaks that result in blunt ends on both strands C) causing linear ends of the newly replicated DNA to circularize D) adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn E) adding numerous GC pairs which resist hydrolysis and maintain chromosome integrity

D) adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn

The elongation of the leading strand during DNA synthesis A) progresses away from the replication fork. B) occurs in the 3' → 5' direction. C) produces Okazaki fragments. D) depends on the action of DNA polymerase. E) does not require a template strand.

D) depends on the action of DNA polymerase.

Which component of the complex described enters the exit tunnel through the large subunit of the ribosome? A) tRNA with attached lysine (#1) B) tRNA with polypeptide (#2) C) tRNA that no longer has attached amino acid D) newly formed polypeptide E) initiation and elongation factors

D) newly formed polypeptide

Which of the following is a function of a signal peptide? A) to direct an mRNA molecule into the cisternal space of the ER B) to bind RNA polymerase to DNA and initiate transcription C) to terminate translation of the messenger RNA D) to translocate polypeptides across the ER membrane E) to signal the initiation of transcription

D) to translocate polypeptides across the ER membrane

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base? A) One of the daughter cells, but not the other, would have radioactive DNA. B) Neither of the two daughter cells would be radioactive. C) All four bases of the DNA would be radioactive. D) Radioactive thymine would pair with nonradioactive guanine. E) DNA in both daughter cells would be radioactive.

E) DNA in both daughter cells would be radioactive

A new DNA strand elongates only in the 5' to 3' direction because A) DNA polymerase begins adding nucleotides at the 5' end of the template. B) Okazaki fragments prevent elongation in the 3' to 5' direction. C) the polarity of the DNA molecule prevents addition of nucleotides at the 3' end. D) replication must progress toward the replication fork. E) DNA polymerase can only add nucleotides to the free 3' end.

E) DNA polymerase can only add nucleotides to the free 3' end.

Which of the enzymes synthesizes short segments of RNA? A) I B) II C) III D) IV E) V

E) V

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the A) binding of ribosomes to mRNA. B) shape of the A and P sites of ribosomes. C) bonding of the anticodon to the codon. D) attachment of amino acids to tRNAs. E) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs

E) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs

A frameshift mutation could result from A) a base insertion only. B) a base deletion only. C) a base substitution only. D) deletion of three consecutive bases. E) either an insertion or a deletion of a base.

E) either an insertion or a deletion of a base.

To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act? A) exonuclease, DNA polymerase III, RNA primase B) helicase, DNA polymerase I, DNA ligase C) DNA ligase, nuclease, helicase D) DNA polymerase I, DNA polymerase III, DNA ligase E) endonuclease, DNA polymerase I, DNA ligase

E) endonuclease, DNA polymerase I, DNA ligase