hey there. i have been given a practice exam for my exam coming up in 2 weeks. its 55 questions but the ones i have posted here i am not sure about my answer. any help would be appreciated. thx
1.
The following steps are required for DNA replication. What is the second step?
a. DNA ligase joins DNA fragments
b. an RNA primer is synthesized
c. DNA polymerase removes the RNA primer
d. a replication fork forms
my answer:D
2.
Which of the following statements is false?
a. DNA polymerase joins nucleotides in one direction only.
b. The leading strand of DNA is made continuously.
c. The lagging strand of DNA is started by an RNA primer.
d. DNA replication proceeds in one direction around the bacterial chromosome.
e. Multiple replication forks are possible on a bacterial chromosome.
My answer: B
3.
rRNA, tRNA, and mRNA are all encoded by genes in the prokaryotic chromosome. Which of these three have a purely structural function (does not code for an enzyme)?
a. rRNA
b. tRNA
c. mRNA
d. All of these
e. Both a and b.
My answer:D
4.
The following steps occur during translation. What is the fourth step?
a. a tRNA with an amino acid binds to the A site
b. the ribosome comes apart
c. the ribosome forms on mRNA
d. a peptide bond forms
My Answer:A
5.
Which of the following is not a step in translation?
a. Initiation at the AUG start codon
b. Pairing of codons with anticodons
c. Joining of the Okazaki fragments
d. Transport of amino acids by tRNA's
My Answer: C
6.
Use the following genetic code to determine the DNA sequence of methionine-lysine- proline-stop: AAA – lysine AUG – methionine CCC – proline UAA – stop UAC – tyrosine
a. AUGAAACCCUAA – 3’
b. UACUUUGGGAUU – 3’
c. TTAGGGTTTCAT – 3’
d. UUAGGGUUUCAU – 3’
e. TACTTTGGGATT-3’
My Answer:D
7.
From the previous problem, what would the transfer RNA (tRNA) sequence look like?
a. UACUUUGGGAUU – 3’
b. TACTTTGGGATT-3’
c. AUGAAACCCUAA – 3’
d. UUAGGGUUUCAU – 3’
My Answer C
8.
If a single base substitution occurred in the third position of the UAA codon above, going from A to C, what would happen to the polypeptide?
a. Nothing, the polypeptide would still be methionine-lysine-proline-stop.
b. The polypeptide would at least be methionine-lysine-proline-tyrosine.
c. The polypeptide would most likely have a longer polypeptide sequence.
d. Both b and c.
My Answer: B
9.
Two bacterial cells in the same colony have the following codon sequences for an enzyme that is involved in changing glucose 6-phosphate to fructose 6-phosphate in glycolysis. Bacteria 1 = CGU – arginine; Bacteria 2 = CGC – arginine
What can you say about these bacterial cells?
a. Their genotypes are the same.
b. Their phenotypes are different.
c. Their genotypes are different.
d. Degeneracy in the genetic code enables their phenotypes to remain the same.
e. Both c and d.
My Answer: B
10.
In the previous problem, the phenotype is not something you can see. How would you be able to know that they have different codon sequences for this enzyme?
a. You would not know unless you sequenced their genes for this enzyme.
b. Grow them on media that contains fructose 6-phosphate.
c. You could amplify their gene sequences with PCR, cut them with a restriction enzyme recognizing the sequence CGC only, and separate and compare their banding patterns using agarose gel electrophoresis.
d. All of the above.
e. a and c.
My Answer:E
11.
A mutagen:
a. is a chemical that can directly or indirectly bring about a mutation.
b. can be physical in nature like gamma radiation.
c. interacts with DNA to cause damage or errors.
d. alters DNA at random locations.
e. All of the above.
My Answer: E
12.
Spontaneous mutations:
a. can arise as a result of mistakes in DNA replication.
b. occur in the absence of any mutation-causing agents.
c. can arise as a result of a defective or absent DNA repair enzyme.
d. All of the above.
My Answer: D
13.
All of the following are ways in which mutagens can act on DNA EXCEPT?
a. Some cause adjacent thymidine dimers.
b. Some act as nucleoside analogs causing altered base-pairing properties.
c. Some act on DNA repair enzymes preventing them from working.
d. Some cause chemical alterations of nitrogenous bases causing them to have altered base-pairing properties.
e. Some cause deletions or insertions of DNA causing frameshift mutations.
My Answer:B
14.
Spontaneous mutations:
a. occur more often than induced (mutagen-caused) mutations.
b. occur approximately once in a million replicated genes.
c. occur randomly along a chromosome.
d. are one way in which evolution of a species can occur.
e. b, c, and d above.
My Answer:E
15.
What ultimately gives rise to different alleles of a gene?
a. transformation
b. chromosomes
c. spontaneous mutation
d. induced (chemical or physical agents) mutation
e. Both c and d.
My Answer:C
16.
Some humans have an increased sensitivity to UV light because they have a genetic defect in nucleotide excision repair. This results in an increased risk for skin cancer. These people have:
a. xeroderma pigmentosum
b. photolyase
c. nucleoside analogs
d. carcinogens
My Answer:B
17. (
An auxotroph
a. is any mutant microorganism having a nutritional requirement that is absent in the parent.
b. does not require any supplemental nutrients.
c. has all of the same functional enzymes as its parent.
d. Both b and c.
My Answer:D
18.
Carcinogens:
a. are mutagens.
b. are substances that cause cancer in animals.
c. can be detected by a quick and inexpensive screening procedure called the Ames test.
d. can be detected by using histidine auxotrophs of Salmonella.
e. All of the above are true.
My Answer:A
19.
The Ames test is used:
a. to determine if Salmonella can use the amino acid histidine.
b. because animals cannot be used as models for studies of carcinogenicity.
c. to verify that a chemical is carcinogenic.
d. to determine if bacteria develop cancer.
My Answer: C
20.
Exposure of mutant bacteria to mutagenic substances may cause new mutations that reverse the effect (the change in phenotype) of the original mutation. Such bacteria are called:
a. auxotrophs
b. revertants
c. replicants
d. recombinants
My Answer:A
21.
Mutant bacteria can be detected by selecting or testing for an altered phenotype by which of the following methods?
a. Neutral selection – selecting mutant cells on the basis of antibody production.
b. Positive (direct) selection – detection of mutant cells by rejection of the unmutated parental cells.
c. Negative (indirect) selection – selection of cells that cannot perform a certain function using replica plating.
d. Both a and b.
e. Both b and c.
My Answer:D
22.
All of the following are true of plasmids except:
a. They are small, circular molecules of DNA that can carry genes for heavy metal resistance.
b. They are essential for survival of the organism in most situations.
c. They can be transferred between bacteria during conjugation.
d. They may encode genes that enhance the pathogenicity of an organism.
e. They may contain antibiotic resistance genes.
My Answer:C
23.
Which of the following pairs is mismatched?
a. Bacteriocins – plasmid encoded genes responsible for killing other bacteria.
b. Dissimilation plasmid – encodes enzymes that allow for catabolism of unusual sugars or hydrocarbons.
c. Resistance (R) factors – resistance transfer factor (RTF) encodes genes involved in plasmid replication and conjugation.
d. R-determinant – encode genes for pili production and colonization.
e. F factor – carries genes for conjugation pili and for the transfer of the plasmid to other cells.
My Answer: B
24.
All of the following are ways in which prokaryotes can acquire genetic change and evolve EXCEPT?
a. errors in DNA replication
b. plasmids and transposons
c. induced mutation
d. transduction
e. catabolite repression
My Answer:C
25.
Transposons:
a. were discovered in the 1950s by Barbara McClintock.
b. are small pieces of DNA (700 – 40,000 base pairs) that can move from one chromosome to a different location on the same chromosome, different chromosome, or plasmid.
c. can insert themselves within genes, inactivating them.
d. can be simple carrying the gene for transposase or complex carrying the gene(s) for transposase and enterotoxin or antibiotic resistance.
e. All of the above are true for transposons.
My Answer:E
plz let me know i appreciate it thank you
Quick Reply
