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How do mutations mainly occur?
What is a somatic mutation?
A mutation occurring in somatic cells, affecting only the individual.
What are germ-line mutations?
Mutations in sexually reproducing organisms transmitted by gametes to the next generation.
What is a nonsense mutation?
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What is a neutral mutation?
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What is a silent mutation?
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What characterizes a loss of function mutation?
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What defines a lethal mutation?
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Match the types of chromosomal mutations with their descriptions:
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What is a phylogenetic tree?
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What is UPGMA?
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What are mutations?
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Germ-line mutations can be passed to the next generation.
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What is a missense mutation?
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What results from a nonsense mutation?
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What is a neutral mutation?
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A _____ mutation results in the absence or decreased activity of a protein.
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What is a chromosomal mutation?
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What does a phylogenetic tree represent?
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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?
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Which type of chromosomal mutation includes the centromere during inversion?
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What is the result of a nonreciprocal interchromosomal translocation?
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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?
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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?
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What is the effect of an auxotrophic mutation on an organism?
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What characterizes a conditional mutation?
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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?
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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?
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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?
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How do frameshift mutations typically occur?
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What characterizes a back mutation?
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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?
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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?
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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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