Biology 002 Midterm 3 (Ch 6-8)

(Q007) How does the total number of replication origins in bacterial cells compare to the number of origins in human cells?

1 versus 10,000

(Q009) The chromatin structure in eukaryotic cells is much more complicated than that observed in prokaryotic cells. This is thought to be the reason why DNA replication occurs much faster in prokaryotes. How much faster is it?

10×

(Q032) Below is the sequence from the 3´ end of an mRNA. 5´-CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3´ If you were told that this sequence contains the stop codon for the protein encoded by this mRNA, what is the anticodon on the tRNA in the P site of the ribosome when release factor binds to the A site?

5´-CCA-3´ (The stop codon (UAA) is underlined in the mRNA sequence below; this is the only stop codon on this piece of mRNA. The codon (UGG) preceding the stop codon will be binding to a tRNA in the P site of the ribosome when release factor binds to the A site. The anticodon of the tRNA will bind to the codon UGG and will be CCA. 5´-CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3´)

(Q005) If the genome of the bacterium E. coli requires about 20 minutes to replicate itself, how can the genome of the fruit fly Drosophila be replicated in only 3 minutes?

Drosophila DNA contains more origins of replication than E. coli DNA.

(Q023) Which of the following statements is FALSE

Eukaryotic mRNA molecules do not have lifetimes longer than 30 minutes.

(Q038) Which of the following statements about prokaryotic mRNA molecules is FALSE?

Ribosomes must bind to the 5´ cap before initiating translation

(Q008) Which of the following statements correctly explains what it means for DNA replication to be bidirectional?

The replication forks formed at the origin move in opposite directions

(Q011) Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon?

The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter.

(Q022) The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be "overwound" in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication?

Topoisomerases break the covalent bonds of the backbone, allowing the local unwinding of DNA ahead of the replication fork.

(Q029) The piece of RNA below includes the region that codes for the binding site for the initiator tRNA needed in translation. 5´-GUUUCCCGUAUACAUGCGUGCCGGGGGC-3´ Which amino acid will be on the tRNA that is the first to bind to the A site of the ribosome?

arginine

(Q010) DNA polymerase catalyzes the joining of a nucleotide to a growing DNA strand. What prevents this enzyme from catalyzing the reverse reaction?

hydrolysis of pyrophosphate (PPi) to inorganic phosphate (Pi) + Pi

(Q014) You prepare bacterial cell extracts by lysing the cells and removing insoluble debris via centrifugation. These extracts provide the proteins required for DNA replication. Your DNA template is a small, double-stranded circular piece of DNA (a plasmid) with a single origin of replication and a single replication termination site. The termination site is on the opposite side of the plasmid from the origin. What part of the DNA replication process would be most directly affected if a strain of bacteria lacking helicase were used to make the cell extracts?

initiation of DNA synthesis (Because helicase unwinds the two DNA template strands, replication of both strands depends upon the activity of helicase at the time of initiation)

(Q020) DNA polymerases are processive, which means that they remain tightly associated with the template strand while moving rapidly and adding nucleotides to the growing daughter strand. Which piece of the replication machinery accounts for this characteristic?

sliding clamp

(Q001) The process of DNA replication requires that each of the parental DNA strands be used as a __________ to produce a duplicate of the opposing strand

template

(Q028) Human beings with the inherited disease xeroderma pigmentosum have serious problems with lesions on their skin and often develop skin cancer with repeated exposure to sunlight. What type of DNA damage is not being recognized in the cells of these individuals?

ultraviolet irradiation damage