1.) Choose the best response for each.
a.) The Ames test is commonly used to test whether a particular chemical is mutagenic. When you conduct an Ames test, you need two groups of plates. One group of plates contains bacteria that are exposed to the chemical of interest, while the other plates contain bacteria that are not exposed to the chemical. Why is the latter group needed if you are just interested in the rate of mutation caused by the chemical?
The group without the chemical can be exposed to mammalian liver extract to see the effects of liver enzymes on the bacteria. Having two groups allows researchers to compare the effects of different environments on the mutation rate It is important to compare the rate of mutations with the chemical to the normal background mutation rate. Mutations occur spontaneously even without the presence of a mutagen. The second group is used as a control to make sure that the replica plating technique is done correctly.
b.) Frameshift mutations can be very severe. What is one reason why they are often so serious?
When a frameshift mutation occurs, it causes transition mutations to occur. These are particularly severe. When a frameshift mutation occurs, it causes changes in many bases downstream and can affect many of the amino acids in the protein. Frameshift mutations always occur in the regulatory region, so they cause a gene to be turned off and then the protein is not produced at all. When a frameshift mutation occurs, it causes changes in many bases upstream and can affect many of the amino acids in the protein.
c.) An organism that cannot synthesize methionine is called __________.
a mutant a prototroph an auxotroph an autotroph
1.) Choose the best response for each.
a.) The Ames test is commonly used to test whether a particular chemical is mutagenic. When you conduct an Ames test, you need two groups of plates. One group of plates contains bacteria that are exposed to the chemical of interest, while the other plates contain bacteria that are not exposed to the chemical. Why is the latter group needed if you are just interested in the rate of mutation caused by the chemical?
The group without the chemical can be exposed to mammalian liver extract to see the effects of liver enzymes on the bacteria. |
Having two groups allows researchers to compare the effects of different environments on the mutation rate |
It is important to compare the rate of mutations with the chemical to the normal background mutation rate. Mutations occur spontaneously even without the presence of a mutagen. |
The second group is used as a control to make sure that the replica plating technique is done correctly. |
b.) Frameshift mutations can be very severe. What is one reason why they are often so serious?
When a frameshift mutation occurs, it causes transition mutations to occur. These are particularly severe. |
When a frameshift mutation occurs, it causes changes in many bases downstream and can affect many of the amino acids in the protein. |
Frameshift mutations always occur in the regulatory region, so they cause a gene to be turned off and then the protein is not produced at all. |
When a frameshift mutation occurs, it causes changes in many bases upstream and can affect many of the amino acids in the protein. |
c.) An organism that cannot synthesize methionine is called __________.
a mutant |
a prototroph |
an auxotroph |
an autotroph |
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Related questions
1. At Thanksgiving dinner, your great aunt refuses to eat with plastic silverware and proudly exclaims that she has discarded all plastics because âthey cause cancer.â You wonder if chemicals you commonly use are mutagenic. You recall your time in BY 331, Genetics, and realize that you can use the Ames test to test for reversion of a point mutation in the HisG gene in the bacteria S. typhimurium. You added the chemical you wish to test into the growth medium for the bacteria. You carefully plated an equal number of cells on each mutagenesis plate. You also calculated percent survival for chemical treated cells relative to untreated cells. Remember that the plate media for survival is not selective. A summary of the results is shown below.
Chemical | Percent Survival | Number of Revertants (# of His+ colonies/selective plate) |
No chemical added | 100 | 28 |
Chemical A | 50 | 1400 |
Chemical B | 70 | 20 |
Chemical C | 100 | 7 |
A. What medium must be used in the selective plate as part of the Ames test? Explain how a mutation gives rise to a revertant in this experiment.
[Type your answer here, use as much space as necessary to completely answer the question]
B. You are initially surprised to see revertants in the absence of any chemical that you are testing, but you realize that this is normal. Explain a specific way in which a revertant can arise in the absence of an added mutagen.
[Type your answer here, use as much space as necessary to completely answer the question]
C. Which chemicals would you identify as containing a mutagen? Explain your reasoning.
[Type your answer here, use as much space as necessary to completely answer the question]
D. Which chemicals would you identify as possibly antimutagenic? Explain your reasoning.
[Type your answer here, use as much space as necessary to completely answer the question]
QUESTION 1
A mutation caused by exposure to gamma rays is called a spontaneous mutation
a. | True | |
b. | False | |
c. | Sometimes, depending on the type of base change | |
d. | Gamma rays do not cause mutations |
QUESTION 2
A recessive mutation affecting an essential biochemical pathway can be detected________
a. | when the organism is heterozygous for that mutation. | |
b. | when the organism is homozygous for that mutation. | |
c. | in either homozygous or heterozygous conditions. | |
d. | only by sequencing (recessive mutations never show a phenotype). |
QUESTION 3
During DNA replication, the newly synthesized chain grows by adding
a. | nitrogenous bases | |
b. | the sugar-phosphate backbone | |
c. | nucleosides | |
d. | dNTPs |
QUESTION 4
During replication, the DNA strand 5â- AAGTCTAGCCTAG -3â will serve as a template for the polymerization of:
a. | 5â- CTAGGCTAGACTT -3â | |
b. | 5â - TTCAGATCGGATC -3â | |
c. | 5â - GATCCGATCTGAA -3â | |
d. | 3â - AAGTCTAGCCTAG -5â |
QUESTIOn 5
Given the following DNA sequences, select which statement(s) is(are) correct.
Sequence 1:
5â-TGGACGCTAA-3â
3â-ACCTGCGATT-5â
Sequence 2:
5â-AATCGCAGGT-3â
3â-TTAGCGTCCA-5â
Sequence 3:
5â-ACCTGCGATT-3â
3â-TGGACGCTAA-5â
a. | Sequences 1 and 2 are the same | |
b. | Sequences 1 and 3 are the same | |
c. | Sequences 2 and 3 are the same | |
d. | Sequences 1, 2 and 3 are all different |
QUESTION 6
Repetitive sequences in the genome are hotspots for:
a. | Deamination | |
b. | Depurination | |
c. | Thymine dimer formation | |
d. | Replication errors |
QUESTION 7
Select which statement(s) about the Ames test is(are) correct
a. | it has been designed to understand mutation repair systems in Salmonella typhimurium | |
b. | it uses mammalian liver extract | |
c. | it allows to study whether chemical compounds or their enzymatic breakdown products are mutagenic | |
d. | it is based on whether a chemical compound causes reversion mutations from his+ to his- | |
e. | two of the above are correct | |
f. | three of the above are correct |
QUESTION 8
Select which statement(s) is(are) correct.
a. | All DNA strands have a direction, and it is specified by the carbons in the sugar backbone. | |
b. | All DNA strands have a direction, and it is specified by hydrogen bonds between nucleotides. | |
c. | In order to form proper base pairs in a double stranded DNA molecule, the two strands must run in opposite directions. | |
d. | A and C are correct. | |
e. | B and C are correct. |
QUESTION 9
Studies of gene mutation frequencies have shown that:
a. | mutations are rare, and genomes are generally stable. | |
b. | mutation frequencies differ among organisms and also between genes, suggesting certain genes are more susceptible to mutation. | |
c. | mutation frequencies are consistent between organisms, and each region of DNA is equally susceptible to random mutations. | |
d. | Both A and B are correct. | |
e. | Both A and C are correct. |
QUESTION 10
The compound 5-bromodeoxyuridine (BrdU) is a derivative of uracil, and if BrdU becomes incorporated during DNA replication, it pairs with adenine. This compound is best classified as which type of mutagen?
a. | base analog | |
b. | base inducer | |
c. | intercalating agent | |
d. | oxidative agent | |
e. | alkylating agent |
QUESTION 11
The rate of mutation of the fruit fly is higher than the rate of mutation of Algae
True
False
QUESTION 12
Thymine dimers are most commonly caused by which of the following?
a. | X-rays | |
b. | Alkylating agents | |
c. | U.V. irradiation | |
d. | DNA intercalating agents |
QUESTION 13
What chemical group is found in the 3â end of a DNA strand?
a. | an alcohol | |
b. | a hydroxyl | |
c. | a methyl | |
d. | a phosphate |
QUESTION 14
What chemical group is found in the 5â end of a DNA strand?
a. | an alcohol | |
b. | a hydroxyl | |
c. | a methyl | |
d. | a phosphate |
QUESTION 15
Which is the correct order of molecules binding to DNA during DNA replication?
a. | Helicase, SSB, primase, DNA pol III, DNA pol I, ligase | |
b. | SSB, DNA pol I, ligase, helicase, DNA pol I, primase | |
c. | primase, helicase, DNA pol III, ligase, DNA pol I, SSB | |
d. | SSB, helicase, primase, DNA pol III, DNA pol I, ligase |
QUESTION 16
Which statement(s) is(are) correct about strand slippage?
a. | It can cause disorders such as Huntingon disease. | |
b. | It is a process that causes mutations altering the number of DNA repeats. | |
c. | It is a process that incorporates nucleotide base analogs and trinucleotide repeats. | |
d. | a and b are correct. | |
e. | b and c are correct. | |
f. | a, b and c are correct. |
help needed asap.