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Questions and Answers
What is referred to as forward mutation?
What is referred to as forward mutation?
What type of mutation involves the substitution of one base pair for another or the insertion or deletion of one or a few nucleotide pairs at a specific site in a gene?
What type of mutation involves the substitution of one base pair for another or the insertion or deletion of one or a few nucleotide pairs at a specific site in a gene?
What is the result of a nonsense mutation?
What is the result of a nonsense mutation?
What type of mutation occurs when a second mutation restores the original phenotype lost due to an earlier mutation?
What type of mutation occurs when a second mutation restores the original phenotype lost due to an earlier mutation?
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What type of mutation involves the substitution of one purine for another or one pyrimidine for another?
What type of mutation involves the substitution of one purine for another or one pyrimidine for another?
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What is the result of a suppressor mutation?
What is the result of a suppressor mutation?
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What can occur at distinct sites in the same gene as the original mutation or in different genes, even on different chromosomes?
What can occur at distinct sites in the same gene as the original mutation or in different genes, even on different chromosomes?
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What is the consequence of a mutation occurring in a primordial germ-line cell?
What is the consequence of a mutation occurring in a primordial germ-line cell?
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What is the characteristic of somatic mutations?
What is the characteristic of somatic mutations?
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What is a genetic polymorphism?
What is a genetic polymorphism?
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What is the average frequency of Single Nucleotide Polymorphisms (SNPs) in the human genome?
What is the average frequency of Single Nucleotide Polymorphisms (SNPs) in the human genome?
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What is the characteristic of insertion-deletion polymorphisms (indels)?
What is the characteristic of insertion-deletion polymorphisms (indels)?
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What is the term for stretches of DNA consisting of units of two, three, or four nucleotides?
What is the term for stretches of DNA consisting of units of two, three, or four nucleotides?
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Why is there a high degree of genetic diversity in human populations?
Why is there a high degree of genetic diversity in human populations?
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What is the ultimate source of all genetic variation?
What is the ultimate source of all genetic variation?
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What type of mutation affects the number of chromosomes in the cell?
What type of mutation affects the number of chromosomes in the cell?
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What is the term for a sudden, heritable change in the genotype of a cell or an organism?
What is the term for a sudden, heritable change in the genotype of a cell or an organism?
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What would occur if alleles did not exist?
What would occur if alleles did not exist?
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What is the consequence of mutations occurring too frequently?
What is the consequence of mutations occurring too frequently?
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What is the result of a mutation in an organism?
What is the result of a mutation in an organism?
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What is the term for an organism that exhibits a novel phenotype resulting from a mutation?
What is the term for an organism that exhibits a novel phenotype resulting from a mutation?
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What type of mutation affects the number of intact chromosomes, resulting in aneuploidy?
What type of mutation affects the number of intact chromosomes, resulting in aneuploidy?
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Which type of mutation has the highest frequency of occurrence in humans?
Which type of mutation has the highest frequency of occurrence in humans?
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What is the result of a missegregation of a chromosome pair during meiosis?
What is the result of a missegregation of a chromosome pair during meiosis?
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Which type of mutation involves changes in the DNA sequence of the nuclear or mitochondrial genomes?
Which type of mutation involves changes in the DNA sequence of the nuclear or mitochondrial genomes?
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What is the frequency of chromosome mutations per cell division?
What is the frequency of chromosome mutations per cell division?
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What is the consequence of many genome mutations during development?
What is the consequence of many genome mutations during development?
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Which types of mutations are frequently seen in cancer cells?
Which types of mutations are frequently seen in cancer cells?
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What is the result of a base substitution, deletion, or insertion in a codon?
What is the result of a base substitution, deletion, or insertion in a codon?
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Which type of mutation is responsible for conditions such as trisomy 21?
Which type of mutation is responsible for conditions such as trisomy 21?
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Study Notes
Mutation and Genetic Variation
- Mutations can occur in primordial germ-line cells, which can result in multiple gametes receiving the mutant gene, increasing its chances of perpetuation.
- The likelihood of a mutant allele being manifested in an organism depends on the dominance of the allele and the stage in the reproductive cycle at which the mutation occurs.
- Mutations in DNA can be passed on to future generations if they occur in cells that will populate the germline.
Human Genetic Diversity
- Genetic diversity and individuality have been maintained throughout evolution due to the steady influx of new nucleotide variation.
- A variant is considered a genetic polymorphism if it is found in more than 1% of chromosomes in the general population.
- Alleles with frequencies of less than 1% are considered rare variants.
Types of Polymorphism
- There are many types of polymorphisms, including those resulting from deletions, duplications, triplications, and other variations of hundreds to millions of base pairs of DNA.
- Some polymorphisms are not associated with a known disease phenotype, while others are rare variants that cause serious illness.
Single Nucleotide Polymorphisms (SNPs)
- SNPs usually have only two alleles, corresponding to different bases occupying a particular location in the genome.
- SNPs are common, occurring on average once every 1000 base pairs, resulting in around 3,000,000 differences between any two human genomes.
Insertion-Deletion Polymorphisms
- Indels are caused by the insertion or deletion of between 2 and 100 nucleotides.
- There are hundreds of thousands of indels in the genome, which can be simple (having only two alleles) or multiallelic.
Microsatellites
- Microsatellites are stretches of DNA consisting of units of two, three, or four nucleotides.
- They are a type of multiallelic indel that can be further subdivided into microsatellite and minisatellite polymorphisms.
Mutation
- Mutations are inherited changes in the genetic material that provide new genetic variation, allowing organisms to evolve.
- Genetic information is accurately duplicated during DNA replication, but heritable changes can occur due to mutations.
- Mutations can be classified into three categories: genome mutations, chromosome mutations, and gene mutations.
Types of Mutations
- Genome mutations affect the number of chromosomes in the cell.
- Chromosome mutations alter the structure of individual chromosomes.
- Gene mutations alter individual genes, including point mutations (nucleotide substitutions, insertions, or deletions).
- RNA processing mutations affect the splicing of introns and exons.
- Nucleotide substitutions can result in missense mutations, chain termination mutations, or RNA processing mutations.
Consequences of Mutations
- Mutations can result in the creation of new alleles, leading to genetic diversity.
- Without mutation, genes would exist in only one form, and populations would not be able to evolve or adapt to environmental changes.
- Mutations can also disrupt the faithful transfer of genetic information from generation to generation.
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Description
Explore how mutations in primordial germ-line cells can affect gametes and influence the likelihood of manifestation in an organism. Learn about the role of dominance and reproductive cycle stage in determining mutation perpetuation.
