ANSWERS TO EXAMINATION TWO PRACTICE QUESTIONS

True or false: Either F+ or Hfr cells are required to act as the donor if transformation is going to occur.
Explanation:F+ and Hfr cells may act as donors in conjugation, not transformation, because they produce sex pili.
Because the progeny each receive one old DNA strand and one newly synthesized DNA strand, DNA replication is said to be
The base which forms hydrogen bonds with thymine in DNA is
Explanation:Thymine and adenine are complementary in DNA, as are guanine and cytosine. Uracil is found only in RNA, not in DNA.
Coliforms are Gram-positive rods.
Explanation: Coliforms are Gram-negative rods that inhabit the intestines of animals, including humans.
Salmonella infections can be acquired through handling pet turtles
Explanation: Reptiles, including turtles, often harbor Salmonella bacteria. It is important to wash your hands after handling them.
Mannitol salt agar is an example of media which is
Explanation: Mannitol salt agar has a high salt concentration, which inhibits most other gram-positive cocci besides Staphylococcus from growing on it. This makes it selective. Mannitol salt agar also contains a pH indicator that changes color when acidic. Thus it turns from pink to yellow when mannitol is fermented. This makes it differential.
"Clap" is a street name used for the disease
Explanation: Gonorrhea is also sometimes referred to as "GC", which stands for "gonococcus".
When a bacteria acquires a new gene that has come floating in solution and migrated into the cell, this process is called
Explanation: Conjugation requires cell-to-cell contact between two bacteria. One cell must have a sex pili. Transduction is when a virus transfer DNA from one bacteria to another. Replication is when DNA makes a copy of itself.
Infections with Salmonella are usually
Explanation: Salmonella causes food poisoning. It is usally contracted from undercooked or improperly prepared foods.
If a mutation occurs in a segment of DNA, it is most likely to affect
Explanation:By definition, a mutation is permanent, inheritable change in the DNA. Thus, it would be expected to pass down to all future progeny.
The enzyme used in genetic engineering to open a plasmid and produce "sticky ends" is called a
Explanation:DNA polymerase is the enzyme used to join nucleotides to synthesize DNA. Lipase is the enzyme used to degrade lipids. Transcriptase would be an enzyme involved in transcription. Ligase is an enzyme that "glues" DNA pieces together.
Restriction endonucleases would be expected to cut
Explanation: Restriction endonucleases cut DNA. Both plasmids and chromosomes are made of DNA.
Agrobacterium tumefaciens causes crown gall tumors. It has been used as a genetic engineering tool to move genes into
Explanation: Agrobacterium tumefaciens has successfully used to move genes into monocots.
The following steps must be performed to make a bacterium produce human interferon:
1-Translation
2-Restriction endonuclease
3-Procaryotic transcription
4 - DNA ligase
5-Transformation
6-Eucaryotic transcription
7 - Reverse transcriptase
Put the steps in the correct sequence.
Explanation:The human gene that codes for interferon must undergo transcription in order to make a mRNA copy of itself. However, this copy would contain introns (DNA "garbage") that must be cut out before the bacteria could use the mRNA. Once the introns are removed, the mRNA that results could be exposed to reverse transcriptase. Then this strand of mRNA would code for a piece of DNA that has no introns in it. A restriction endonuclease could be used to cleave this "cleaned up" gene and cleave a plasmid so they both end in the same "sticky ends". DNA ligase would be used to seal the plasmid to the gene, once the gene has inserted itself into the plasmid. This chimera (combination of plasmid and insulin gene) can be taken up by a living bacterial cell through transformation (DNA coming across in solution into a competent cell). This transformed bacteria would copy the directions in this DNA into mRNA, which is transcription. The mRNA would go to the ribosome and direct the synthesis of interferon. This is translation.
Describe how the Polymerase Chain Reaction (PCR) technique could be used to conduct a test for hepatitis B. Identify each specific step used in its proper sequence.
Explanation: A body sample would be collected from the patient (e.g. blood) where the suspected pathogen would be expected to be incubating. It would contain DNA from many sources. The DNA sequences to be copied can be greater than 100 base pairs long. If no selection was undertaken, all the DNA that is present would be copied by the following PCR procedure.
The DNA would first be denatured (made single-stranded). At a cold temperature, primers would then be added to the DNA so they bind to it. DNA polymerases and nucleotides would then be added. The mixture would be subjected to high heat. A copy of each DNA strand would be made. These steps would be repeated many times. In 20 PCR cycles, one million copies of the target DNA sequence would be produced.
For diagnostic purposes, a fluorescent monoclonal antibody to Hepatitis B could be used. If DNA from Hepatitis B was present in the patient's sample, it would fluoresce after PCR. The fluorescent antibody would bind only to Hepatitis B DNA. If the patient had no Hepatitis B viral DNA present, there would be no binding.
Griffith's experiment with Streptococcus pneumoniae demonstrated that the process of ___________can occur in certain bacteria.
Answer: transformation
Explanation:Griffith was able to demonstrate that dead Streptococcus pneumoniae bacteria with capsules passed the capsule gene in solution to live bacteria through transformation.
A baby born to a mother with ________ really needs silver nitrate drops or erythromycin put into their eyes soon after birth to prevent blindness.
Explanation: Gonorrheal opthalmia neonatorum is gonorrhea of the eye in newborns. It can be contracted during birth when the mother has Neisseria gonorrhoeae in the birth canal. Silver nitrate drops are ususally effective at controlling Neisseria. Erythromycin may be used instead to also combat Chlamydia trachomatis, which can also lead to blindness.
If gene A mutates at a rate of 10 -2 per cell division, gene B mutates at a rate of 10 -7 per cell division, what is that chance that both genes will mutate in the same cell?
Explanation: The mutation rate for two genes simultaneously mutating is calculated by multiplying the exponents of the separate mutation rates for each gene being considered. To multiply exponents, you add them. Thus, -2 plus -7 equals -9.
When a nitrogen base is added to the DNA, this causes a ____________ mutation.
Explanation: Frameshift mutations can result from either adding or deleting a nitrogen base from DNA.
___________, which has been associated with Mexican-style soft cheeses, can cause premature delivery in pregnant women.
Explanation: All the bacteria listed cause food poisoning, but only Listeria has been associated with Mexican-style soft cheeses.
Hemophilus influenzae type b is of greatest concern in ________________.
Explanation: In young children, Hemophilus influenzae type b infections may lead to meningitis and death.
The first recombinant DNA experiment was performed by Herbert Boyer and Stanley Cohen. In their experiment, they moved a gene from a _______ to a ________ cell.
Explanation: DNA was moved from a toad into E.coli bacteria.
The symptoms of food poisoning show up very quickly (usually within one to six hours after ingestion) when a person is infected with __________ because this bacteria produces a toxin. Other bacteria responsible for food poisoning usually require at least twelve hours for symptoms to appear because the bacteria must first multiply in the person.
Explanation: Shigella, Salmonella, and Staphylococcus all cause food poisoning. However Shigella and Salmonella cause symptoms when the bacteria multiply. This takes time. Staphylococcus symptoms come from a toxin that is already present in the food when you eat it because the Staph synthesized it as it grew in the food.
Chlamydia trachomatis is a ________________.
Explanation: Chlamydia is an unusual bacteria because it it is an obligate intracellular parasite. It won't grow on any of the lab media scientists have tried. It requires live cells to reproduce. However, it is a bacteria.
A "bacteriophage" is a ________________.
Sickle cell anemia is due to a _______ mutation in the gene that codes for the beta chain in hemoglobin.
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