Term
| Mutations in DNA (Pros and Cons) |
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Definition
Pros
-phenotypic variability
-adaptation to environmental changes
-evolution
Cons
-cell death
-genetic disease
-cancer |
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Term
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Definition
-a change in the total number of chromosomes
-the deletion or duplication of genes or segments of a chromosome
-rearrangements of the genetic material either within or among chromosomes |
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Term
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Definition
| mutations occurring in the base pair sequence of DNA within individual genes |
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Term
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Definition
happen naturally and randomly and are usually linked to normal biological or chemical processes in the organism.
-Rates of spontaneous mutations vary among loci in different organisms |
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Term
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Definition
| result from the influence of an extraneous factor, either natural or artificial. |
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Term
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Definition
| occur in any cell except germ cells and are not heritable. |
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Term
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Definition
| occur in gametes and are inherited. |
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Term
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Definition
| occur within genes located on the autosomes |
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Term
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Definition
| occur within genes located on the X chromosome |
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Term
| When a recessive autosomal mutation occurs in a somatic cell of a diploid organism |
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Definition
| it is unlikely to result in a detectable phenotype. |
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Term
| Inherited dominant autosomal mutations |
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Definition
| will be expressed phenotypically in the first generation. |
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Term
| X-linked recessive mutations |
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Definition
| arising in the gametes of a homogametic female may be expressed in hemizygous male offspring |
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Term
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Definition
| are base substitutions in which one base pair is altered. |
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Term
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Definition
| change a codon resulting in an altered amino acid within a protein-coding portion of a gene. |
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Term
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Definition
| changes a codon into a stop codon and results in premature termination of translation. |
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Term
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Definition
| alters a codon but does not result in a change in the amino acid at that position of the protein. |
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Term
| a transition has occurred when... |
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Definition
| If a pyrimidine replaces a pyrimidine or a purine replaces a purine |
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Term
| a transversion has occurred when... |
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Definition
| If a purine and a pyrimidine are interchanged |
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Term
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Definition
result from insertions or deletions of a base pair
occurs when any number of bases are added or deleted, except multiples of three, which would reestablish the initial frame of reading. |
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Term
Mutations can be classified according to their phenotypic effects
loss-of-function
gain-of-function
neutral |
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Definition
loss-of-function
reduces or eliminates function of the gene product
gain-of-function
gene product has enhanced or new functions
neutral
do not affect gene products or gene expression;
occur in noncoding regions of the genome that do not contain genes
represent the majority of all mutations |
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Term
| These types of errors predominantly lead to point mutations |
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Definition
DNA polymerase occasionally inserts incorrect nucleotides, generally due to mispairing.
Although DNA polymerase has 3’ to 5’ exonuclease proofreading capacity, sometimes errors are not corrected |
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Term
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Definition
a reversible isomerization in a molecule, brought about by a shift in the location of a hydrogen atom
amino (-NH2) can tautomerize to imino (=NH)
keto (-C=O) can tautomerize to enol (=C-OH)
in nucleotides can result in mutations due to anomalous base pairing |
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Term
| DNA base damage by depurination and deamination is the most common cause of spontaneous mutation |
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Definition
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Term
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Definition
| loss of one of the nitrogenous bases in an intact double-helical DNA molecule |
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Term
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Definition
| an amino group in cytosine or adenine is converted to a keto group |
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Term
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Definition
are natural or artificial agents that induce mutations.
Base Analogs
Alkylating Agents
Acridine Dyes
UV light
Ionizing Radiation |
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Term
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Definition
| can substitute for purines or pyrimidines during nucleic acid replication |
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Term
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Definition
| donate an alkyl group to amino or keto groups in nucleotides to alter base-pairing affinity |
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Term
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Definition
| cause frameshift mutations by intercalating between purines and pyrimidines. |
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Term
| UV radiation creates pyrimidine dimers |
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Definition
| that distort the DNA conformation in such a way that errors tend to be introduced during DNA replication |
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Term
| Base Excision Repair and Nucleotide Excision Repair |
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Definition
In both:
damage is excised
original DNA sequence is restored by DNA polymerase that uses the undamaged strand as its template
remaining break in the double helix is sealed.
The two pathways differ in the way in which the damage is removed from DNA. |
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Term
Base excision repair (BER)
acts on single bases that are damaged |
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Definition
1. DNA N-glycosylase removes damaged base by cleaving N-glycosidic bond and creates “AP” site—apurinic or apyrimidic site
apurinic—missing purine base;
apyrimidic—missing a pyrimidine base
backbone intact, just base is missing
2. AP endonuclease cleaves the phosphodiester backbone
3. DNA polymerase, DNA ligase—fills the gap; seals “nick”
Base excision repair (BER) involves:
recognition of the erroneous base by DNA glycosylase
cutting of the DNA backbone by AP endonuclease |
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Term
Nucleotide excision repair (NER)
repairs larger regions of damage (including pyrimidine dimers in humans) |
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Definition
Endonucleases + Exonucleases “patrol” DNA—
remove a short stretch of DNA surrounding damage
DNA polymerase fills in gap
DNA ligase seals nick
Nucleotide excision repair (NER) repairs bulky lesions |
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Term
| DNA double-strand break (DSB) |
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Definition
repair is activated when both DNA strands are cleaved.
It is responsible for reannealing the two strands. |
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Term
| Non-homologous End Joining |
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Definition
Repair mechanism for double-stranded DNA
breaks (i.e. from ionizing radiation)
Very error prone and mutagenic
Results in chromosome translocations
-Cell tries to put back pieces to form 46
chromosomes, but there is no template for end joining when both strands are broken!
-So, fragments of chromosomes put back together in the wrong order. |
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Term
| Homologous Recombination Repair |
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Definition
recombination between homologous chromosomes (or sister chromatids)
to patch double-stranded breaks or replication blockage on one chromosome |
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Term
Which of the following categories of mutations are not possible to pass to offspring?
A) silent
B) somatic
C) frameshift
D) induced
E) X-linked |
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Definition
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Term
Neutral mutations
A) do not alter the product of a gene.
B) occur frequently in noncoding regions of the genome.
C) can be used to estimate mutation rates.
D) are expected to accumulate over time.
E) All of the above. |
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Definition
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Term
Base excision repair begins with recognition of a chemically altered base by
A) DNA polymerase
B) AP endonuclease
C) DNA ligase
D) DNA glycosylase
E) uvr gene products |
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Definition
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Term
Which of the following can result in frameshift mutations?
A) alkylating agent
B) tautomeric shift
C) base analog
D) acridine dye
E) deamination |
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Definition
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