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Questions and Answers
Which type of mutation involves the replacement of one amino acid in a protein?
Which type of mutation involves the replacement of one amino acid in a protein?
A frameshift mutation occurs due to a substitution of one nucleotide.
A frameshift mutation occurs due to a substitution of one nucleotide.
False
What happens in a nonsense mutation?
What happens in a nonsense mutation?
A premature stop codon is created, resulting in truncated proteins.
In sickle cell disease, glutamic acid is replaced by ________ due to a point mutation.
In sickle cell disease, glutamic acid is replaced by ________ due to a point mutation.
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Which of the following mutations leads to an alteration in the reading frame of the genetic code?
Which of the following mutations leads to an alteration in the reading frame of the genetic code?
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Silent mutations result in the change of an amino acid due to redundancy in the genetic code.
Silent mutations result in the change of an amino acid due to redundancy in the genetic code.
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What mutation is characterized by the insertion of multiple CAG repeats?
What mutation is characterized by the insertion of multiple CAG repeats?
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Match the type of mutation with its description:
Match the type of mutation with its description:
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What are environmental agents that cause mutations called?
What are environmental agents that cause mutations called?
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Spontaneous mutations are caused by environmental agents.
Spontaneous mutations are caused by environmental agents.
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Name one type of radiation that is classified as ionizing radiation.
Name one type of radiation that is classified as ionizing radiation.
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Exposure to _______ can result in the formation of DNA adducts.
Exposure to _______ can result in the formation of DNA adducts.
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Match the following chemical mutagens with their characteristics:
Match the following chemical mutagens with their characteristics:
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Which condition is characterized by extreme sensitivity to ultraviolet light and a high frequency of skin cancer?
Which condition is characterized by extreme sensitivity to ultraviolet light and a high frequency of skin cancer?
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Mismatch repair (MMR) corrects mismatched bases introduced during DNA replication.
Mismatch repair (MMR) corrects mismatched bases introduced during DNA replication.
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What type of cancer is associated with mutations in MMR genes?
What type of cancer is associated with mutations in MMR genes?
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Mutations in the gene encoding the DNA glycosylase MYH can cause an autosomal recessive form of __________ cancer.
Mutations in the gene encoding the DNA glycosylase MYH can cause an autosomal recessive form of __________ cancer.
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Match the following DNA repair mechanisms or conditions with their descriptions:
Match the following DNA repair mechanisms or conditions with their descriptions:
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What is a potential consequence of DNA double-strand breaks if not repaired?
What is a potential consequence of DNA double-strand breaks if not repaired?
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Lynch Syndrome is also known as hereditary non-polyposis colorectal cancer.
Lynch Syndrome is also known as hereditary non-polyposis colorectal cancer.
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What type of radiation can induce breakage of DNA strands?
What type of radiation can induce breakage of DNA strands?
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What type of repeat expansion is associated with Huntington disease?
What type of repeat expansion is associated with Huntington disease?
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Fragile X syndrome is caused by a CAG repeat expansion.
Fragile X syndrome is caused by a CAG repeat expansion.
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Which gene is associated with Myotonic dystrophy?
Which gene is associated with Myotonic dystrophy?
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The gene __________ is affected in Fragile X syndrome.
The gene __________ is affected in Fragile X syndrome.
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Match the following genetic disorders with their corresponding features:
Match the following genetic disorders with their corresponding features:
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What is a dominant-negative mutation?
What is a dominant-negative mutation?
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Splice mutations lead to the production of functional mRNA.
Splice mutations lead to the production of functional mRNA.
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Name one condition caused by an alteration in the nucleotide sequence required for splicing.
Name one condition caused by an alteration in the nucleotide sequence required for splicing.
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What condition results from an extra X chromosome in males?
What condition results from an extra X chromosome in males?
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Uniparental disomy can lead to Prader-Willi Syndrome if two copies of chromosome 15 are inherited from the mother.
Uniparental disomy can lead to Prader-Willi Syndrome if two copies of chromosome 15 are inherited from the mother.
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Name one common cause of chromosomal mutations.
Name one common cause of chromosomal mutations.
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Chromosomal mutations can be detected through ___ techniques.
Chromosomal mutations can be detected through ___ techniques.
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Which technique uses fluorescent probes to identify specific mutations in chromosomes?
Which technique uses fluorescent probes to identify specific mutations in chromosomes?
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Structural chromosomal mutations can potentially lead to infertility.
Structural chromosomal mutations can potentially lead to infertility.
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What syndrome is caused by chromosomal abnormalities and results in developmental challenges?
What syndrome is caused by chromosomal abnormalities and results in developmental challenges?
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Match the following conditions with their causes:
Match the following conditions with their causes:
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Study Notes
DNA Repair Mechanisms
- Xeroderma Pigmentosum (XP) is caused by mutations in genes encoding proteins involved in DNA repair. Individuals with XP are extremely sensitive to ultraviolet (UV) light, leading to a high frequency of skin cancer.
- Lynch Syndrome is caused by mutations in mismatch repair (MMR) genes, resulting in a high mutation rate and increased risk of colorectal cancer.
- Double-strand DNA breaks are lethal if not repaired. Post replication repair corrects these breaks.
- Mismatch Repair (MMR) corrects mismatched bases introduced during DNA replication. Mutations in MMR genes are linked to Lynch Syndrome, the most common type of hereditary colorectal cancer.
Gene Mutations by Mechanism
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Substitution: Changes in a single nucleotide
- Transition: Purine for purine (A ↔ G) or pyrimidine for pyrimidine (T ↔ C)
- Transversion: Purine for pyrimidine (or vice versa)
- Insertions and Deletions: Addition or removal of one or more nucleotide pairs.
- Frameshift Mutations: Insertions or deletions that shift the reading frame, altering protein structure and function.
- Nonsense Mutation: Point mutation that creates a premature stop codon, leading to nonfunctional, truncated proteins.
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Missense Mutation: Point mutation that replaces one amino acid with another.
- Example: Sickle cell disease, where valine replaces glutamic acid in the hemoglobin protein.
- Silent Mutation: Point mutation that does not alter the resulting amino acid due to redundancy in the genetic code.
Examples of Gene Mutations and Their Effects
- Sickle Cell Anemia: A single nucleotide change in the HBB gene (GAG to GTG) results in the substitution of glutamic acid with valine in the beta-globin protein, leading to abnormal hemoglobin and red blood cells.
- Huntington’s Disease: Multiple CAG trinucleotide repeats in the HTT gene lead to an abnormal huntingtin protein, causing neurodegeneration.
- Fragile X Syndrome: A CGG repeat expansion in the FMR1 gene results in methylation of promoter sequences and lack of expression of the FMR1 protein.
Ribonucleotide Repeat Expansion Diseases
- Huntington Disease: Autosomal dominant inheritance, CAG repeats in the HTT gene on chromosome 4, leading to chorea, akinesia, cognitive decline, and behavioral changes.
- Fragile X Syndrome: X-linked dominant inheritance, CGG repeats in the FMR1 gene on chromosome X, leading to distinctive facial features, intellectual disability, and large testes.
- Myotonic Dystrophy: Autosomal dominant inheritance, CTG repeats in the DMPK gene on chromosome 19, leading to muscle weakness, cataracts, premature hair loss, and heart rhythm abnormalities.
Splice Mutations
- Alterations in nucleotide sequences required for splicing, resulting in defective mRNA and shortened proteins.
- Examples include: some forms of β-thalassemia, Gaucher disease, Marfan syndrome, dementia, and epilepsy.
Dominant-Negative Mutations
- Produce nonfunctional proteins that impair the function of normal proteins encoded by the wild-type allele.
- Example: Mutant, nonfunctional p53 binding to DNA, preventing the attachment of functional p53 protein.
Chromosomal Mutations
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Causes:
- Errors in meiosis (non-disjunction)
- Exposure to mutagens (radiation, chemicals, drugs)
- Inherited mutations
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Detection:
- Karyotyping: Photographing chromosomes during cell division to detect abnormalities.
- Fluorescent In Situ Hybridization (FISH): Uses fluorescent probes to detect specific mutations.
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Consequences:
- Developmental disorders (Down syndrome, Turner syndrome)
- Cancer (Chronic Myeloid Leukemia)
- Infertility
Mutations and Mutagenesis
- Spontaneous mutations: Occur naturally due to errors in cell division or DNA replication.
- Mutagens: Environmental agents that cause mutations, including ionizing radiation and chemical mutagens.
Radiation
- Ionizing radiation includes X-rays, γ-rays, α particles, β particles, and neutrons.
- Different forms of radiation have varying penetrating power, with α particles having the least penetration and γ-rays having the most.
Chemical Mutagens
- Chemical mutagenesis may be more important than radiation in producing genetic damage in humans.
- Examples of chemical mutagens include mustard gas, formaldehyde, benzene, dyes, and food additives.
- Exposure to chemicals can lead to DNA adducts, chromosome breaks, and aneuploidy.
DNA Repair
- Essential for preventing the accumulation of mutations.
- Defects in DNA repair mechanisms contribute to various diseases, including cancer and developmental disorders.
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Description
Test your knowledge on DNA repair mechanisms and the genetic disorders associated with them, such as Xeroderma Pigmentosum and Lynch Syndrome. This quiz covers the various types of gene mutations, including substitutions, insertions, and deletions. Challenge yourself and deepen your understanding of these critical biological processes.
