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Questions and Answers
How do mutations mainly occur?
How do mutations mainly occur?
What is a somatic mutation?
What is a somatic mutation?
A mutation occurring in somatic cells, affecting only the individual.
What are germ-line mutations?
What are germ-line mutations?
Mutations in sexually reproducing organisms transmitted by gametes to the next generation.
What is a nonsense mutation?
What is a nonsense mutation?
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What is a neutral mutation?
What is a neutral mutation?
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What is a silent mutation?
What is a silent mutation?
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What characterizes a loss of function mutation?
What characterizes a loss of function mutation?
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What defines a lethal mutation?
What defines a lethal mutation?
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Match the types of chromosomal mutations with their descriptions:
Match the types of chromosomal mutations with their descriptions:
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What is a phylogenetic tree?
What is a phylogenetic tree?
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What is UPGMA?
What is UPGMA?
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What are mutations?
What are mutations?
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Germ-line mutations can be passed to the next generation.
Germ-line mutations can be passed to the next generation.
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What is a missense mutation?
What is a missense mutation?
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What results from a nonsense mutation?
What results from a nonsense mutation?
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What is a neutral mutation?
What is a neutral mutation?
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A _____ mutation results in the absence or decreased activity of a protein.
A _____ mutation results in the absence or decreased activity of a protein.
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What is a chromosomal mutation?
What is a chromosomal mutation?
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What does a phylogenetic tree represent?
What does a phylogenetic tree represent?
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Which method is used to create a phylogenetic tree?
Which method is used to create a phylogenetic tree?
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What type of chromosomal deletion occurs at the end of a chromosome?
What type of chromosomal deletion occurs at the end of a chromosome?
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Which type of chromosomal mutation includes the centromere during inversion?
Which type of chromosomal mutation includes the centromere during inversion?
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What is the result of a nonreciprocal interchromosomal translocation?
What is the result of a nonreciprocal interchromosomal translocation?
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What characterizes a tandem duplication?
What characterizes a tandem duplication?
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What type of chromosomal mutation involves the inversion of a segment by 180 degrees without including the centromere?
What type of chromosomal mutation involves the inversion of a segment by 180 degrees without including the centromere?
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What type of mutation changes a mutant gene back to a wild-type gene at the same site?
What type of mutation changes a mutant gene back to a wild-type gene at the same site?
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Which type of mutation compensates for the original mutation but does not reverse it?
Which type of mutation compensates for the original mutation but does not reverse it?
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What is the effect of an auxotrophic mutation on an organism?
What is the effect of an auxotrophic mutation on an organism?
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What characterizes a conditional mutation?
What characterizes a conditional mutation?
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A null mutation is defined as a mutation that results in:
A null mutation is defined as a mutation that results in:
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What type of mutation involves changes in the chromosome structure, such as deletions?
What type of mutation involves changes in the chromosome structure, such as deletions?
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Which mutation is characterized by the alteration of a body segment's identity?
Which mutation is characterized by the alteration of a body segment's identity?
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Frame mutations result from insertions or deletions of which multiples of base pairs?
Frame mutations result from insertions or deletions of which multiples of base pairs?
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What type of mutation specifically does not alter the amino acid sequence of a protein?
What type of mutation specifically does not alter the amino acid sequence of a protein?
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Which mutation would likely lead to a nonfunctional polypeptide chain due to premature termination of translation?
Which mutation would likely lead to a nonfunctional polypeptide chain due to premature termination of translation?
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How do frameshift mutations typically occur?
How do frameshift mutations typically occur?
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What characterizes a back mutation?
What characterizes a back mutation?
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Which mutation type could affect gene expression by either blocking or activating transcription?
Which mutation type could affect gene expression by either blocking or activating transcription?
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What is the main effect of a missense mutation?
What is the main effect of a missense mutation?
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Which type of mutation results in the production of an altered protein that may not perform its normal function?
Which type of mutation results in the production of an altered protein that may not perform its normal function?
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What type of mutation can only affect the individual and not be passed to future generations?
What type of mutation can only affect the individual and not be passed to future generations?
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Study Notes
Mutations
- A mutation alters the base pair sequence of a gene
- Mutations can be spontaneous or induced by radiation or chemicals
- A cell with a mutation is a mutant cell
- Mutations are heritable changes
Types of Mutations
- Somatic mutations occur in somatic cells and affect only the individual, not passed on to offspring
- Germ-line mutations occur in sexually reproducing organisms and are transmitted to offspring via gametes
Gene Mutations
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Substitution mutations change a single base pair
- Missense mutations change an mRNA codon, resulting in a different amino acid being inserted into the polypeptide. Phenotypic changes may or may not occur.
- Nonsense mutations change an mRNA codon to a stop codon, causing premature termination of polypeptide synthesis. This often results in nonfunctional polypeptide chains.
- Neutral mutations change an mRNA codon but have no detectable effect on protein function. This happens when a new codon codes for a similar amino acid.
- Promoter mutations can block or activate transcription.
- Splice-site mutations can block splicing or create new splicing signals. This can lead to the deletion of part of a protein.
- Silent mutations alter a codon in the mRNA but specify the same amino acid in the protein.
- Back mutations are reverse mutations that restore the original gene sequence.
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Insertion/deletion mutations add or remove base pairs
- Frameshift mutations occur when base pairs are added or removed in a protein-coding gene. This alters the reading frame of the mRNA, leading to the insertion of incorrect amino acids, a shortened or lengthened polypeptide chain, or a nonfunctional polypeptide chain. Frameshift mutations happen when the number of insertions or deletions is not divisible by 3.
Other Mutations
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Point mutations are mutations at a single base pair. There are two types:
- Forward mutations change a wild-type gene to a mutant gene.
- Reverse mutations change a mutant gene back to a wild-type gene.
- True reversion changes a mutant gene to the wild-type amino acid.
- Partial reversion changes a mutant gene to a different amino acid.
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Suppressor mutations mask or compensate for an original mutation. They do not reverse the original mutation, and usually occur at a second site.
- Intragenic suppressor mutations occur within the same gene.
- Intergenic suppressor mutations occur in a different gene.
Mutation Effects
- Visible mutations alter the morphology or visual appearance of an organism.
- Auxotrophic mutations affect a cell's growth.
- Conditional mutations result in the wild-type phenotype under certain conditions. One example is temperature-sensitive mutations.
- Loss-of-function mutations lead to the absence or decreased activity of a protein. These mutations are usually recessive.
- Null mutations result in a nonfunctional protein. They reduce gene expression to zero.
- Spontaneous mutations occur naturally during DNA replication or other stages of cell growth and division.
- Induced mutations are caused by exposure to chemical or physical agents called mutagens.
- Homeotic mutations alter the identity of a body segment, transforming it into a copy of a different segment.
- Lethal mutations cause cell death.
- Frame mutations are insertions or deletions of multiples of 3 base pairs. They cause a shift in the reading frame.
Chromosomal Mutations
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Changes in parts of a chromosome or whole chromosome.
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Occur in both eukaryotes and prokaryotes.
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Can be spontaneous or induced.
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Deletions occur when a part of a chromosome is missing. They are often induced by heat, viruses, or chemicals.
- Acentric chromosomes are chromosomes that have lost the centromere.
- Terminal deletions occur at the end of a chromosome.
- Microdeletions are small deletions.
- Interstitial deletions occur within the interior of a chromosome.
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Duplications are a doubling of a segment of a chromosome.
- Tandem duplications occur when duplicated segments are adjacent to each other.
- Reverse tandem duplications occur when duplicated segments are arranged in the opposite order of the original.
- Terminal tandem duplications occur when duplicated segments are arranged in tandem at the end of the chromosome.
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Inversions occur when a segment of a chromosome is inverted 180 degrees.
- Paracentric inversions do not include the centromere.
- Pericentric inversions include the centromere.
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Translocations involve moving a segment of a chromosome to a different location in the genome.
- Nonreciprocal intrachromosomal translocations move a segment within the same chromosome.
- Nonreciprocal interchromosomal translocations move a segment to a different chromosome.
- Reciprocal interchromosomal translocations involve the exchange of two segments between different chromosomes.
Mutations
- A mutation is an alteration in the base pair sequence of DNA.
- Mutations can be spontaneous or induced.
- Spontaneous mutations occur naturally during DNA replication or other stages of cell growth and division.
- Induced mutations happen when an organism is exposed to a mutagen, which can be a chemical or physical agent.
- Mutations can be classified as somatic or germ-line mutations.
- Somatic mutations affect only the individual and are not passed on to the next generation.
- Germ-line mutations occur in sexually reproducing organisms and can be transmitted by gametes to the next generation.
Types of Gene Mutations
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Substitution: A single base pair is replaced with another.
- Missense mutation: Results in a different amino acid being inserted into the polypeptide chain, which may or may not lead to a phenotypic change.
- Nonsense mutation: Changes the codon to a stop codon, causing premature termination of polypeptide synthesis.
- Neutral mutation: The new codon codes for a chemically equivalent amino acid, leading to no detectable change in protein function.
- Silent mutation: The altered codon specifies the same amino acid in the protein, having no effect on the protein sequence.
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Insertion/Deletion: One or more base pairs are added or removed from the DNA sequence.
- Frameshift mutations: Alter the reading frame of the mRNA, leading to incorrect amino acid insertions or deletions. These mutations can result in nonfunctional proteins.
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Point mutations: Changes to a single base pair.
- Forward mutation: Changes a wild-type gene to a mutant gene.
- Reverse mutation: Changes a mutant gene back to the wild-type.
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Other types:
- Promoter mutation: Can block or activate transcription.
- Splice site mutation: Can block splicing or create new splicing signals, resulting in a protein lacking some of its functional parts.
- Suppressor mutation: Masks or compensates for the original mutation.
- Visible mutation: Affects the morphology or visual appearance of the organism.
- Auxotrophic mutation: Affects cell growth.
- Conditional mutation: Results in the wild-type phenotype but under certain conditions, such as temperature.
- Loss of function mutation: Leads to an absence or decrease in the activity of a protein.
- Null mutation: Results in a protein with no function.
- Homeotic mutation: Alters the identity of certain body segments, transforming them into a copy of a different segment.
- Lethal mutation: Causes cell death.
- Frame mutation: Insertions or deletions that are not multiples of three base pairs, causing a shift in the reading frame.
Chromosomal Mutations
- These mutations involve changes in parts of a chromosome or the whole chromosome.
- They occur in both eukaryotes and prokaryotes.
- Examples include:
- Deletion: Loss of a segment of a chromosome.
- Duplication: Doubling of a segment of a chromosome.
- Inversion: A segment of a chromosome is inverted 180 degrees.
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Translocation: A segment of a chromosome is moved to a different location in the genome.
- Intrachromosomal: Changes position within the same chromosome.
- Interchromosomal: Changes position from one chromosome to another.
- Reciprocal: Two segments from different chromosomes switch with each other.
- These mutations can be spontaneous or induced.
Phylogenetic Trees
- Phylogenetic trees are graphical representations of the evolutionary relationships amongst a group of species or genes.
- Branches represent ancestral organisms.
- UPGMA is a method used to construct phylogenetic trees.
Wild type
- Refers to the standard allele or phenotype of an organism
- Typically observed in wild populations
- Used as a reference point for comparison
Mutations
- Changes in the base pair sequence of DNA
- Result in mutant cells which can be heritable
- Can occur spontaneously or be induced by mutagens
- Occur during DNA replication or other stages of cell division
Types Of Mutations
- Somatic mutations occur in somatic cells
- Affect only the individual and are not inherited
- Germ-line mutations occur in germ cells
- Transmitted to offspring through gametes
Gene Mutations
-
Substitution mutations involve a change in a single base pair
- Missense mutations result in a different amino acid being inserted into the polypeptide chain
- Nonsense mutations change a codon to a stop codon, prematurely terminating polypeptide synthesis
- Neutral mutations result in no detectable functional change in the protein
- Promoter mutations can block or activate transcription
- Splice site mutations can block or create new splicing signals
- Silent mutations change the codon but do not alter the amino acid sequence
- Insertion/deletion mutations involve the addition or removal of base pairs
- Frameshift mutations result from insertions or deletions that are not multiples of three
- Cause the reading frame of the mRNA to shift, potentially resulting in incorrect amino acids, shortened chains, or nonfunctional proteins
Chromosomal Mutations
- Changes that affect parts or entire chromosomes
- Occur in both eukaryotes and prokaryotes
- Can be spontaneous or induced
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Deletion is the loss of a chromosome segment
- Terminal deletions occur towards the end of the chromosome
- Micro deletions are small deletions
- Interstitial deletions occur within the chromosome
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Duplication is the doubling of a chromosome segment
- Tandem duplication involves adjacent duplicated segments
- Reverse tandem duplication involves duplicated segments in the opposite order
- Terminal tandem duplication involves duplicated segments at the end of the chromosome
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Inversion involves a segment of the chromosome being flipped 180 degrees
- Paracentric inversions do not include the centromere
- Pericentric inversions include the centromere
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Translocations involve the movement of a chromosome segment to a different location
- Nonreciprocal intrachromosomal translocations involve a change in position within the same chromosome
- Nonreciprocal interchromosomal translocations involve a change in position from one chromosome to another
- Reciprocal interchromosomal translocations involve the exchange of segments between two different chromosomes
Phylogenetic Trees
- Graphical representations of evolutionary relationships between species or genes
- Branches represent ancestral organisms
- Constructed using methods like UPGMA (Unweighted Pair Group Method with Arithmetic Mean)
Back Mutation
- A reverse mutation that restores the original gene sequence after a mutation
- Used in models like the Jukes-Cantor model to calculate the actual number of mutations that occurred
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