Unit 4 (chap 18, 19, 20, 25, 26) Flashcards
A nucleotide in a DNA strand was depurinated. What type of DNA repair mechanism could be used to repair this nucleotide?
direct repair
Consider the following original DNA strand and mutant DNA strand. Which of the following would best characterize the mutation in the polypeptide strand?
Original: 5’-TTTCCCGGGAAA- 3’
Mutant: 5’-TTTGGGAAA- 3’
- in-frame mutation
- frameshift mutation
- nonsense mutation
- missense mutation
in frame mutation
Classify each definition or example as a somatic mutation, gametic (germline) mutation, or both.
-The mutation arises in the gametes of the individual and is transmitted to the progeny
- Mutations can be caused by an alteration in the DNA sequence
-The mutation affects only the individual in which the mutation occurs and is not passed on to the progeny
- A particular tobacco leaf becomes discolored due to a mutation halfway through the life of the plant
-A man receives a pelvic X-ray. Nine months later, his child is born with a chromosomal abnormality.
Somatic mutation:
A particular tobacco leaf becomes discolored due to a mutation halfway through the life of the plant
The mutation affects only the individual in which the mutation occurs and is not passed on to the progeny
Germline Mutation:
A man receives a pelvic X-ray. Nine months later, his child is born with a chromosomal abnormality.
The mutation arises in the gametes of the individual and is transmitted to the progeny
Both:
Mutations can be caused by an alteration in the DNA sequence
Which of the following can be mutagenic? Select all that apply.
transposons
ionizing radiation
base analogs
UV radiation
intercalating agents
transposons
ionizing radiation
base analogs
UV radiation
intercalating agents
(all of them)
Categorize the following base substitutions as transition mutations or transversion mutations:
C to a T
G to a T
T to an A
T to a C
C to an A
A to a G
G to an A
G to a C
Transition Mutation:
A to a G
C to a T
T to a C
G to an A
Transversion Mutation:
T to an A
C to an A
G to a C
G to a T
Which type of DNA mutation results in a change in the reading frame of an mRNA?
deletion of a single nucleotide
deletion of a single codon
substitution of one codon for another
substitution of one nucleotide with another
Deletion of a single nucleotide
A DNA non‑template sequence reads: 5’ A T G A A G C G C T C A G T A 3’
If a thymine was substituted for nucleotide 6, this would be called a _______ and would result in a ________.
If a guanine was substituted for nucleotide 11, this would be called a _______ and would result in a __________.
If a guanine was substituted for nucleotide 15, this would be called a _______ and would result in a _______.
If a thymine was substituted for nucleotide 6, this would be called a transversion and would result in a missense mutation.
If a guanine was substituted for nucleotide 11, this would be called a transversion and would result in a nonsense mutation.
If a guanine was substituted for nucleotide 15, this would be called a transition and would result in a silent mutation
Strand slippage can cause: (select all that apply)
deletions
insertions
trinucleotide repeats
frameshift mutation
base substitutions
deletions
insertions
trinucleotide repeats
frameshift mutation
Define mutation
an inherited change in the DNA sequence of genetic information
what is the difference between a germline mutation and a somatic mutation
somatic mutations arise in somatic tissues, that do not produce gametes.
germ-line mutations arise in cells that produce gametes and they are passed on to future generations
what is the difference between a gene mutation and a chromosome mutation
a chromosome mutation is a large-scale alteration that affects chromosome structure or the number of chromosomes
a gene mutation are relatively small DNA lesions that affect a single gene
what is a base substitution
an alteration of a single nucleotide in the DNA. It can be a transition or a transversion
what is the difference between a transition and a transversion
transitions are when a purine is replaced by a different purine or a pyrimidine is replaced by a different pyrimidine.
transversions are when a purine is replaced by a pyrimidine or a pyrimidine is replaced by a purine.
Transitions are more likely to happen than transversions
what are insertions and deletions, and what type of mutations do these cause
insertions and deletions are collectively called indels
insertions and deletions are the addition or removal of one or more nucleotide pairs.
these can cause frameshift mutations: changes in the reading frame of the gene. Frameshift mutations usually alter all amino acids encoded by the nucleotides following the mutation.
what are in-frame insertions and deletions and how do they arise
insertions or deletions consisting of any multiple of 3 nucleotides leaves the reading frame intact.
what are expanding nucleotide repeats
mutations where the number of copies of a set of nucleotides increases.
The number of copies of the repeat often correlates with the severity or age of onset of the disease.
How can strand slippage cause the expansion of nucleotide repeats
strand slippage is the misalignment of the sequences or stalling of replication.
If a DNA molecule has 8 copies of a CAG repeat, the two strands separate and replicate. In the course of replication, a hairpin forms on the newly synthesized strand, causing part of the template to be replicated twice and increasing the number of repeats on the newly synthesized strand, causing part of the template to be replicated twice and increasing the number of repeats on the newly synthesized strand. The 2 new strands of the new DNA molecule separate. The strand with the extra CAG copies serves as a template for replication. The resulting DNA molecule contains five additional copies of the CAG repeats.
how can expanding nucleotide repeats correspond to anticipation
Number of copies of the repeat also correlates with its instability: when more repeats are present, the probability of expansion is more to even more repeats increases.
diseases caused by expanding nucleotide repeats gets more severe with each generation (attenuation)
what are the three effects base substitutions can have on the amino acid sequence
Missense mutation: the new codon encodes a different amino acid; there is a change in amino acid sequence
Nonsense mutation: The new codon is a stop codon; there is a premature termination of translation
Silent mutation: The new codon encodes the same amino acid; there is no change in amino acid sequence
what is the difference between a forward mutation and a reverse mutation
a forward mutation alters the wild-type phenotype to a mutant
a reverse mutation changes a mutant phenotype back into the wild type.
what is a neutral mutation
a missense mutation that alters the amino acid sequence of a protein but does not significantly alter its function.
What is a loss of function mutation
these are mutations that cause partial or complete loss of normal protein function. This mutation alters the structure of the protein that the protein no longer works anymore.
what is a gain of function mutation
this mutation causes the cell to produce a protein or gene product whose function is not normally present. Gain of function mutations are frequently dominant in their expression because a single copy of the mutation leads to the presence of a new gene product.
what is a conditional mutation
conditional mutations are expressed only under certain conditions