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Questions and Answers
What is a mutation?
Which type of mutation can be passed on to offspring?
Which of the following is NOT true about somatic mutations?
What does mosaicism refer to in genetics?
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Which mechanism describes a substitution mutation?
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What is the primary cause of most mutations?
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What effect does a missense mutation have on proteins?
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Which condition is an example of chromosomal mosaicism?
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What distinguishes chimerism from mosaicism?
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Which mutation is associated with Achondroplasia?
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What characterizes a silent mutation?
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In which condition does a trinucleotide repeat expansion occur?
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What is the result of the point mutation associated with Sickle Cell Anemia?
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What are the potential consequences of unrepairable DNA mutations?
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Which enzyme is responsible for sealing breaks in DNA during repair?
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What condition is caused by mutations in genes associated with DNA repair mechanisms?
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What type of DNA damage does mismatch repair (MMR) primarily address?
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Which repair process is used to correct single abnormal bases in DNA?
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What increases the mutation rate in cells defective in mismatch repair?
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Which of the following can lead to double-strand breaks in DNA?
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What genetic syndrome is associated with a higher risk of colorectal cancer due to MMR gene mutations?
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What type of mutation results in the substitution of one amino acid for another in a protein?
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Which mutation is characterized by a premature stop codon that results in a truncated protein?
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What is a common consequence of frameshift mutations?
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Which mutation is primarily responsible for Sickle Cell Disease?
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What type of mutation involves the addition of one or more nucleotide pairs?
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Which mutation example is correctly paired with its condition?
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What describes a silent mutation?
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Which of the following is true about transversion mutations?
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What kind of mutations can be inherited from parents to offspring?
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What is the primary purpose of karyotyping?
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Which of the following techniques utilizes fluorescent probes for detecting chromosomal mutations?
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Which of these is NOT a consequence of chromosomal mutations?
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What are spontaneous mutations thought to arise from?
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Which type of radiation is known for having high penetrating power?
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Which of the following is considered a chemical mutagen?
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Chronic Myeloid Leukemia (CML) is primarily caused by what type of chromosomal mutation?
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Study Notes
Mutation Definition
- A mutation is a change in the genetic material (DNA) of a cell, affecting either germline or somatic cells.
- Most mutations occur spontaneously due to errors in DNA replication and repair.
- Sequence variants with no obvious effect on phenotype may be termed polymorphisms.
- Somatic mutations cannot be transmitted to offspring.
- Mutations in gonadal tissue or a gamete can be transmitted to future generations.
Types of Mutations by Affected Cell Population
- Germline mutations: Occur in reproductive cells, can be passed on to offspring.
- Somatic mutations: (acquired mutation) Occur in non-reproductive cells, cannot be inherited but can lead to cancer or other diseases.
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Mosaicism: Presence of two or more populations of cells within an organism, each with a different genetic composition.
- Chromosomal mosaicism: Presence of cell populations with different karyotypes in one organism.
- Example: Sex chromosome mosaicism is frequently seen in Turner syndrome.
- Chimerism: Presence of two genetically distinct cell lines that arise from two different zygotes that fused into one single embryo.
Types of Gene Mutations by Mechanism
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Substitution: Change in a single nucleotide.
- Transition: Purine replaced by purine (A ↔ G) or pyrimidine by pyrimidine (T ↔ C).
- Transversion: Purine replaced by pyrimidine or vice versa.
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Insertions and Deletions:
- Insertion: Addition of one or more nucleotide pairs.
- Deletion: Removal of one or more nucleotide pairs.
- Frameshift Mutations: Caused by insertions or deletions that change the reading frame.
- Nonsense Mutation: A point mutation resulting in a premature stop codon, leading to truncated and usually nonfunctional proteins.
- Missense Mutation: A point mutation leading to the substitution of one amino acid for another in the protein product.
- Silent Mutation: A point mutation that does not change the amino acid due to redundancy in the genetic code.
Examples of Gene Mutations
- Sickle cell disease: A single nucleotide change in the HBB gene (GAG to GTG) results in the substitution of glutamic acid with valine in the hemoglobin protein, causing abnormal hemoglobin and red blood cells.
- Huntington’s Disease: Insertion of multiple CAG trinucleotide repeats in the HTT gene leads to the production of an abnormal huntingtin protein, causing neurodegenerative symptoms.
- Cystic Fibrosis: A three-base pair deletion (ΔF508) in the CFTR gene results in a missing phenylalanine, impairing CFTR protein function and causing thick mucus buildup.
- Tay-Sachs Disease: A deletion or insertion of nucleotides in the HEXA gene alters the reading frame, leading to defective production of the enzyme hexosaminidase A, causing lipid accumulation in the brain.
- Duchenne Muscular Dystrophy: A mutation in the DMD gene introduces a premature stop codon, leading to a truncated dystrophin protein, which results in muscle degeneration.
- Achondroplasia: A point mutation in the FGFR3 gene causes a change in amino acid from glycine to arginine, leading to abnormal bone growth and resulting in dwarfism.
- Fragile X Syndrome: Expansion of CGG repeats in the FMR1 gene leads to gene silencing, resulting in intellectual disability and characteristic physical features.
- Huntington disease: Expansion of the CAG repeat in the coding region of the HTT gene results in a protein with an elongated polyglutamine tract, causing toxic aggregates within certain cells.
Chromosomal Mutations
- Inherited Mutations: Some chromosomal mutations can be passed down from parents to offspring if they occur in germ cells.
Detection of Chromosomal Mutations
- Karyotyping: Process of photographing chromosomes during cell division, allows for detecting abnormalities in number and structure. Example: Down syndrome is diagnosed by identifying three copies of chromosome 21 in a karyotype.
- Fluorescent In Situ Hybridization (FISH): Uses fluorescent probes to bind to specific parts of chromosomes, allowing scientists to detect specific mutations like translocations or deletions.
Consequences of Chromosomal Mutations
- Developmental Disorders: Conditions like Down syndrome and Turner syndrome.
- Cancer: Some cancers, such as Chronic Myeloid Leukemia (CML).
- Infertility: Structural chromosomal mutations can interfere with normal meiotic division.
Mutations and Mutagenesis
- Spontaneous mutations: Naturally occurring mutations thought to arise through chance errors in chromosomal division or DNA replication.
- Mutagens: Environmental agents that cause mutations. These include natural or artificial ionising radiation and chemical or physical mutagens.
Radiation
- Ionising radiation includes electromagnetic waves of very short wavelength (x-rays and γ-rays) and high-energy particles.
- X-rays, γ-rays and neutrons have great penetrating power, α particles only penetrate soft tissues to a fraction of a millimeter, and β particles only up to a few millimeters.
Chemical Mutagens
- More important than radiation in producing genetic damage in humans.
- Examples: Mustard gas, formaldehyde, benzene, some basic dyes and food additives.
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Description
This quiz covers the fundamental concepts of genetic mutations, including their definitions, types, and implications. Learn about germline and somatic mutations, as well as the phenomenon of mosaicism. Understand how mutations impact cellular function and inheritance.
