quiz 2

Which sequence of events is most CORRECT for the initiation and elongation steps of translation? (1) initiator tRNA binds start codon on mRNA (2) small ribosomal subunit binds to mRNA (3) large ribosomal subunit binds (4) tRNA entry and peptidyl transfer reaction (5) translocation of ribosome and release of tRNA

2, 1, 3, 4, 5

Which of the following best describes the complete sequence of steps occurring during EVERY cycle of PCR? 1. The primers hybridize to the target DNA. 2. The mixture is heated to a high temperature to denature the double-stranded target DNA. 3. Fresh DNA polymerase is added to the reaction mixture. 4. DNA polymerase extends the primers to make a copy of the target DNA.

2, 1, 4

Use this list of technical steps to answer Questions 17-18. 1. Two cells were fused using a small electrical current. 2. An embryo was implanted into a "surrogate mother". 3. All nuclear DNA was removed from a sperm. 4. A cell was taken from an adult sheep. 5. All nuclear DNA was removed from an egg. Which step was NOT part of producing a cloned animal?

3

If the sequence of amino acids encoded by a strand of DNA is serine-alanine-lysine-leucine, what is the order of bases in the template strand of DNA? (Use the table below.)

3' AGACGTTTCAAT

In which direction does the RNA polymerase move?

3' → 5' along the template strand

What was the order of events in producing a cloned animal?

4, 5, 1, 2

An Okazaki fragment has which of the following arrangements?

5' RNA nucleotides, DNA nucleotides 3'

The following steps must be performed to make a bacterium produce human protein X: 1-Translation; 2-Restriction enzyme; 3-Prokaryotic transcription; 4-DNA ligase; 5-Transformation; 6-Eukaryotic transcription; 7-Reverse transcription. Put the steps in the correct sequence.

6, 7, 2, 4, 5, 3, 1

The 5'- cap of eukaryotic mRNAs is a(n):

7-methylguanosine joined to the mRNA via a 5' → 5' triphosphate linkage.

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

A gene from an organism can theoretically be expressed by any other organism.

Which codon serves as the start codon in mRNA for translation?

AUG

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in the figure would you expect after first round of replication if the DNA was replicated in a conservative manner?

B

Which of the following statements about E. coli RNA polymerase is false?

Core enzyme selectively binds promoter regions, but cannot initiate synthesis without a sigma factor.

Southern blotting is used to detect a specific

DNA

How can the leading and lagging strands be synthesized in a coordinated fashion?

DNA Polymerase works as a dimer, and the looped lagging strand allows the enzyme to proceed in the same direction with each strand.

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive adenine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA in both daughter cells would be radioactive.

After mixing a heat-killed, phosphorescent strain of bacteria with a living nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?

Descendants of the living cells are also phosphorescent.

The use of an antibiotic-resistance gene on a plasmid used in genetic engineering makes

Direct selection possible.

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in the figure above would be expected after two rounds of DNA replication in the presence of 14N?

E

What is the order of the tRNA binding sites on the 70S ribosome with respect to the 5′->3′ direction of the mRNA?

E P A

Which of the following enzymes will produce a blunt end ? (Cut site is indicated by the * in the recognition sequence.)

EcoRV (GAT*ATC)

In animal cloning why is an egg cell required?

Egg proteins are required for embryonic development.

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

Gaps left at the 5' end of the lagging strand

DNA is synthesized in which of the following directions?

In the 5' > 3' direction on both DNA strands.

The function of the dideoxy (dd) nucleotides that are used in the Sanger method of DNA sequencing is to

Incorporate into newly replicated DNA strands and terminate their synthesis

What is the role of DNA ligase during DNA replication?

It joins Okazaki fragments together.

The restriction enzyme EcoRI cuts between the G and the A of the sequence GAATTC. Which statement is true about this enzyme?

It leaves sticky ends of sequence AATT.

What is one of the advantages of producing human growth hormone (HGH) from a cloned gene in a bacterial cell?

Larger quantities are available.

In E. coli, there is a mutation in a gene called dnaB that compromises the helicase activity. Which of the following would you expect as a result of this mutation?

No replication fork will be formed.

Which of these polymerases does not require a template?

Polyadenylate polymerase

At replication forks:

RNA primers are synthesized by primase.

What is the function of topoisomerase?

Relieving strain in the DNA ahead of the replication fork

When a DNA molecule is described as replicating bidirectionally, that means that it has two:

Replication forks.

What is the advantage of producing human factor IX in sheep rather than in bacteria?

Sheep will produce recombinant protein that is chemically more similar to humans.

What is meant by the description "antiparallel" regarding the strands that make up DNA?

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 about the structure or composition of DNA is FALSE?

The amount of thymine closely approximates that of guanine within a particular organism.

Which of the following statements about aminoacyl-tRNA synthetases is false?

The enzyme will use any tRNA species, but is highly specific for a given amino acid.

In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine) for several minutes and then switched to nonradioactive medium. It is then viewed by electron microscopy and autoradiography. The figure represents the results. Grains represent radioactive material within the replicating eye. Which of the following is the most likely interpretation?

There are two replication forks going in opposite directions.

Which choice is an example of "recombinant DNA"?

a bacterial plasmid combined with a human gene

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of two nucleotides

Cellular protein synthesis proceeds in which direction?

amino to carboxyl terminus

What is a clone?

an exact copy of a DNA, cell or organism

RNA polymerase:

can synthesize RNA chains de novo (without a primer).

The sigma factor of E. coli RNA polymerase:

combines with the core enzyme to confer specific binding to a promoter.

A "transgenic" animal

contains a foreign gene.

Processing of a primary mRNA transcript in a eukaryotic cell does not normally involve:

conversion of normal bases to modified bases, such as inosine and pseudouridine.

In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP?

decrease in glucose and increase in cAMP

Microarray technology is a process in which:

genes active within tissues are identified using a complementary DNA probe.

A eukaryotic gene has "sticky ends" produced by the restriction endonuclease BamHI. The gene is added to a mixture containing BamHI and a bacterial plasmid that carries two genes conferring resistance to ampicillin and tetracycline. The plasmid has one recognition site for BamHI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics. Bacteria that contain the plasmid, but not the eukaryotic gene, would grow

in all four types of broth.

The base in the wobble position of a codon:

is the 3´ (third) base.

Which is NOT a part of cloning a human gene into a recombinant plasmid?

removing all the nuclear DNA from a human egg

In his work with pneumonia-causing bacteria and mice, Griffith found that:

some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

Bacteria containing a plasmid into which the eukaryotic gene has integrated would grow in

the ampicillin broth and the nutrient broth.

The lactose operon is likely to be transcribed when:

the cyclic AMP and lactose levels are both high within the cell.

The leading and the lagging strands differ in that:

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.

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that:

the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.

Differential RNA processing may result in:

the production of two distinct proteins from a single gene.

Which of the following is the first event to take place in translation in eukaryotes?

the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

In the large-scale production of a particular human protein in E. coli cells, the cDNA corresponding to the protein was modified so that the expressed protein would have six histidine residues at the C-terminus. The purpose of this modification was

to facilitate purification of the expressed protein though binding to an affinity column containing chelated nickel.