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The following is a list of mutational changes. For each of the specific mutations described, indicate which of the terms in the right-hand column applies, either as a description of the mutation or as a possible cause. More than one term from the right column can apply to each statement in the left column.
| 1. an A-T base pair in the wild-type gene is changed to a G-C pair | a. transition |
| 2. an A-T base pair is changed to a T-A pair | b. base substitution |
| 3. the sequence AAGCTTATCG is changed to AAGCTATCG | c. transversion |
| 4. the sequence AAGCTTATCG is changed to AAGCTTTATCG | d. deletion |
| 5. the sequence AACGTTATCG is changed to AATGTTATCG | e. insertion |
| 6. the sequence AACGTCACACACATCG is changed to AACGTCACATCG | f. deamination |
| g. X-ray irradiation | |
| h. intercalator | |
1.
To determine:
The term that describes “an A-T base pair in the wild-type gene is changed to a G-C pair” among the options given below,
a. transition
b. base substitution
c. transversion
d. deletion
e. insertion
f. deamination
g. X-ray irradiation
h. intercalator
Introduction:
When purines and pyrimidines are exchanged with each other, the process is called transition.
Answer to Problem 1P
Correct answer:
An A-T base pair in the wild-type gene is changed to a G-C pair: transition and base substitution.
Explanation of Solution
In the given mutation, A-T base pair is exchanged with a G-C base pair so it can be a base substitution. This can also be a transition mutation because adenine is a purine which is interchanged with another purine that is guanine. Thymine replaced the cytosine, and both are also pyrimidines. Thus, this condition can be a base substitution mutation or a transition mutation.
2.
To determine:
The term that describes “an A-T base pair is changed to a T-A pair” among the options given below,
a. transition
b. base substitution
c. transversion
d. deletion
e. insertion
f. deamination
g. X-ray irradiation
h. intercalator
Introduction:
When one purine is replaced by pyrimidine in a pair of two bases, the resulting process is called transversion.
Answer to Problem 1P
Correct answer:
an A-T base pair is changed to a T-A pair: base substitution and transversion.
Explanation of Solution
In the given mutation, a base pair ‘A-T’ can be changed to a ‘T-A’ base-pair so the replacement of one purine with pyrimidine can be observed. Thus, the mutation for concerting A-T into T-A can be a transversion. The substitution of A by T is taking place so, it can also be a base substitution mutation.
3.
To determine:
The term that describes “the sequence AAGCTTATCG is changed to AAGCTATCG” among the options given below,
a. transition
b. base substitution
c. transversion
d. deletion
e. insertion
f. deamination
g. X-ray irradiation
h. intercalator
Introduction:
In this particular case, the exposure of X-rays is responsible for deletion mutation from the wild type sequence.
Answer to Problem 1P
Correct answer:
the sequence AAGCTTATCG is changed to AAGCTATCG: deletion and X-ray irradiation.
Explanation of Solution
If both, wild type and mutated sequence are observed that it can be seen that there is a deletion of nitrogenous base T from wild type sequence. The exposure to X-ray irradiation may be responsible for deletion mutation. Thus, the correct match for the given mutation is deletion and X-ray irradiation.
4.
To determine:
The term that describes “the sequence AAGCTTATCG is changed to AAGCTTTATCG” among the options given below,
a. transition
b. base substitution
c. transversion
d. deletion
e. insertion
f. deamination
g. X-ray irradiation
h. intercalator
Introduction:
When one or more nitrogenous bases are removed from the nucleotide sequence, then the process is called deletion.
Answer to Problem 1P
Correct answer:
the sequence AAGCTTATCG is changed to AAGCTTTATCG: deletion and X-ray irradiation.
Explanation of Solution
Observation of wild type and mutated sequence can lead to a conclusion that there is a deletion of nitrogenous base T from wild type sequence. Deletion mutation may happen to because of exposure to X-ray irradiation. Thus, the correct match for the given mutation is deletion and X-ray irradiation.
5.
To determine:
The term that describes “the sequence AACGTTATCG is changed to AATGTTATCG” among the options given below,
a. transition
b. base substitution
c. transversion
d. deletion
e. insertion
f. deamination
g. X-ray irradiation
h. intercalator
Introduction:
Transition is the change of one purine to another purine or one pyrimidine to another pyrimidine.
Answer to Problem 1P
Correct answer:
the sequence AACGTTATCG is changed to AATGTTATCG: base substitution, transition, and deamination.
Explanation of Solution
In the given mutation, base T is exchanged with base C so it can be a base substitution. This can also be a transition mutation because cytosine is a pyrimidine which is interchanged with another pyrimidine that is thymine. Deamination can also be noticed in the given mutation because the conversion of a methylated C to T is taking place. Thus, the correct match for the given mutation is a substitution, transition, and deamination.
6.
To determine:
The term that describes “the sequence AACGTCACACACATCG is changed to AACGTCACATCG” among the options given below,
a. transition
b. base substitution
c. transversion
d. deletion
e. insertion
f. deamination
g. X-ray irradiation
h. intercalator
Introduction:
Crossing over is the process of exchange of genetic material between the sister chromatids at chiasmata.
Answer to Problem 1P
Correct answer:
The sequence AACGTCACACACATCG is changed to AACGTCACATCG: deletion and crossing over.
Explanation of Solution
In the given mutation, it can be noticed that a segment CACACACA has been lost from wild type sequence, so it is representing deletion. A segment can be removed from the wild type gene during the process of crossing over. Thus, the correct match for the given mutation is deletion and crossing over.
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Chapter 7 Solutions
Genetics: From Genes to Genomes, 5th edition
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