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Questions and Answers
Which factor is NOT a direct cause of genetic mutations, as described?
Which factor is NOT a direct cause of genetic mutations, as described?
- Exposure to pathogenic agents such as viruses
- Exposure to physical mutagens
- Errors during DNA replication
- Dietary changes over generations (correct)
A mutation in which type of cell would be inheritable?
A mutation in which type of cell would be inheritable?
- Germinal cells (correct)
- Somatic cells
- Skin cells
- Muscle cells
Which of the following is an example of a chemical mutagen?
Which of the following is an example of a chemical mutagen?
- X-rays
- UV radiation
- 5-bromouracil (correct)
- HPV
Exposure to which type of radiation is most associated with leukemia in radiologists?
Exposure to which type of radiation is most associated with leukemia in radiologists?
A mutation that involves the substitution of a purine base for a pyrimidine base is classified as what type of mutation?
A mutation that involves the substitution of a purine base for a pyrimidine base is classified as what type of mutation?
A mutation results in a codon changing from one that codes for an amino acid to a stop codon. What type of mutation is this?
A mutation results in a codon changing from one that codes for an amino acid to a stop codon. What type of mutation is this?
A mutation occurs in the third base of a codon, but the amino acid sequence of the resulting protein remains unchanged. This is an example of what kind of mutation?
A mutation occurs in the third base of a codon, but the amino acid sequence of the resulting protein remains unchanged. This is an example of what kind of mutation?
What is the primary effect of a frameshift mutation on protein synthesis?
What is the primary effect of a frameshift mutation on protein synthesis?
Which of the following best describes unstable or dynamic mutations?
Which of the following best describes unstable or dynamic mutations?
What genetic characteristic is associated with Fragile X syndrome?
What genetic characteristic is associated with Fragile X syndrome?
Flashcards
Mutations
Mutations
Modifications génétiques face aux différences climatiques, aux ressources nutritionnelles ou aux agents pathogènes.
Agents mutagènes
Agents mutagènes
Agents causant des mutations, comme les substances chimiques, les radiations et les virus.
Mutations ponctuelles
Mutations ponctuelles
Changements au niveau d'un nucléotide, incluant la substitution, la délétion ou l'insertion.
Mutation de transition
Mutation de transition
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Mutation de transversion
Mutation de transversion
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Mutation faux-sens
Mutation faux-sens
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Mutation non-sens
Mutation non-sens
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Mutation silencieuse
Mutation silencieuse
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Mutation FRAMESHIFT
Mutation FRAMESHIFT
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Mutations instables
Mutations instables
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Study Notes
- Genetic modifications in response to climatic differences, nutritional resources, and pathogens are called mutations.
General Information about Mutations
- Mutations are modifications of a nucleotide or DNA sequence.
- Mutations can be natural, due to replication errors or cell divisions, or induced by mutagens like chemicals, radiation or viruses.
- Mutations can affect somatic and germ cells, with germ cell mutations being passed to offspring.
- Mutations can affect non-coding sequences, often without functional impact, or coding sequences, leading to hereditary genetic diseases and cancers.
Mutagenic Agents
- Mutagenic agents cause mutations and can be categorized as follows:
- Chemical substances: nucleotide analogs like 5-bromouracil
- Ultraviolet rays: potentially causing skin cancer
- Ionizing radiation: X-rays (linked to leukemia or sterility in radiologists)
- Viruses: e.g., HPV implicated in cervical cancer
Types of Mutations
- Mutations are divided into two main categories:
- Microlésionnelles mutations: punctual or instable (triplet expansion)
- Macrolésionnelles mutations: affecting chromosomal fragments with multiple genes
- Point mutations: modifications at the nucleotide level involving substitution, deletion, or insertion
Mutations by Substitution
- Two mechanisms cause these mutations:
- Transition mutation: when a purine base is substituted by another purine base, or a pyrimidine base is substituted by another pyrimidine base (A ➜ G or T ➜ C)
- Transversion mutation: when a purine base is substituted by a pyrimidine base, or vice versa
- Base substitution mutations lead to three types of mutations:
- Faux-sens mutations: a single base change leads to a modification of the amino acid, altering the resulting protein, and generally occurring within the first two bases of a codon
- Non-sens (stop) mutations: point mutations modify an amino acid codon into a stop codon, causing premature termination of translation and a shorter, truncated protein, often leading to disease
- Silent (or same sense) mutations: mutations occur at the third base of a codon, resulting in the same amino acid being coded, or affect non-coding regions of DNA or introns
Mutations by Deletion or Insertion (Frameshift Mutation)
- Addition or removal of nucleotides causes a shift in the reading frame, changing multiple amino acids or leading to premature termination via a stop codon
Unstable (Dynamic) Mutations
- Unstable sequences are formed by successive and homogeneous repetitions of a nucleotide motif, e.g., (CAG)n
- In the general population, the number of repetitions is variable but relatively stable, not exceeding a certain level
- Example: Fragile X syndrome, associated with (CGG)n repeats
- Normal: 5-50 repeats
- Premutation: 60-230 repeats
- Full mutation: >230 repeats, leading to the inactivation of the FMR1 gene
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