DNA Repair and Mutation Types

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Questions and Answers

What type of mutation results from the replacement of a purine with a pyrimidine or vice versa?

Silent Mutation

Transversion (correct)

Insertions

Frameshift Mutation

Which mutation type directly results in the premature termination of protein synthesis?

Silent Mutation

Nonsense Mutation (correct)

Missense Mutation

Insertion Mutation

What is the primary consequence of a frameshift mutation?

Production of a truncated protein

Alteration of the reading frame (correct)

Substitution of one nucleotide

Redundancy in the genetic code

What is the consequence of unrepaired DNA mutations?

Serious consequences for the individual and future generations Signup and view all the answers

Sickle cell disease is an example of which type of mutation?

Missense Mutation Signup and view all the answers

Which mutation is primarily involved in the process leading to Huntington's disease?

Insertion Mutation Signup and view all the answers

Which enzyme is primarily responsible for sealing breaks in DNA?

DNA ligase Signup and view all the answers

What does a silent mutation imply about its effect on protein function?

It does not change the amino acid due to redundancy Signup and view all the answers

What condition is associated with mutations in the genes encoding repair proteins from UV damage?

Xeroderma pigmentosum Signup and view all the answers

Which DNA repair mechanism corrects mismatched bases that occur during replication?

Mismatch repair (MMR) Signup and view all the answers

Cystic fibrosis is often caused by which specific type of mutation?

Deletion Mutation Signup and view all the answers

Tay-Sachs disease is associated with which type of mutation event?

Frameshift Mutation Signup and view all the answers

What genetic syndrome is caused by mutations in MMR genes?

Lynch syndrome Signup and view all the answers

Reactive oxygen species primarily contribute to which DNA damage?

Double-strand breaks Signup and view all the answers

Which protein is associated with excising single abnormal bases in DNA repair?

DNA glycosylase MYH Signup and view all the answers

What is one potential effect of chromosome breaks if left unrepaired?

Lethality in the cell Signup and view all the answers

Which trinucleotide repeat is associated with Huntington disease?

CAG Signup and view all the answers

What is a common characteristic of Fragile X syndrome?

Large protruding chin Signup and view all the answers

In which chromosome is the DMPK gene, related to myotonic dystrophy, located?

Chromosome 19 Signup and view all the answers

What type of mutation leads to defective mRNA by altering the nucleotide sequence required for splicing?

Splice mutation Signup and view all the answers

What is a characteristic effect of a dominant-negative mutation?

Inhibition of the normal protein function Signup and view all the answers

BRCA1 and BRCA2 mutations increase the risk for which type of disease?

Cancer Signup and view all the answers

Chromosomal mutations can result in which type of change?

Changes in either structure or number of chromosomes Signup and view all the answers

Which of the following diseases is caused by a mutation in the HBB gene?

Sickle cell anemia Signup and view all the answers

What is the most likely consequence of unbalanced translocations in a pregnancy?

Chromosomal imbalance leading to conditions like Patau syndrome Signup and view all the answers

Which genetic disorder is directly caused by a Robertsonian translocation involving chromosomes 14 and 21?

Down Syndrome Signup and view all the answers

Which of the following accurately describes uniparental disomy and its related syndrome?

Maternal uniparental disomy of chromosome 15 leads to Prader-Willi Syndrome Signup and view all the answers

What is a characteristic symptom of Turner Syndrome?

Short stature Signup and view all the answers

What causes chromosomal mutations during cell division?

Errors in Meiosis Signup and view all the answers

Which factor can lead to structural mutations of chromosomes?

Exposure to mutagens Signup and view all the answers

What is a common effect of trisomy, specifically Trisomy 21?

Intellectual disability and characteristic facial features Signup and view all the answers

Which chromosomal condition is associated with the presence of an extra X chromosome in males?

Klinefelter Syndrome Signup and view all the answers

What is the primary purpose of karyotyping?

To photograph and analyze chromosomes during cell division Signup and view all the answers

What type of chromosomal mutation can lead to infertility?

Both A and B Signup and view all the answers

Which technique employs fluorescent probes to detect chromosomal mutations?

Fluorescent In Situ Hybridization (FISH) Signup and view all the answers

What is the main effect of chromosomal translocations in cancer cells?

Uncontrolled cell growth Signup and view all the answers

Which of the following is NOT a consequence of chromosomal mutations?

Increased fertility Signup and view all the answers

Which of the following correctly classifies spontaneous mutations?

Mutations caused by chance errors in DNA processes Signup and view all the answers

Which type of radiation has the least penetrating power?

Alpha particles Signup and view all the answers

Which of the following is considered a chemical mutagen?

Formaldehyde Signup and view all the answers

Study Notes

DNA Repair

Environmental chemicals may cause DNA damage, leading to mutations.
DNA repair mechanisms involve endonuclease, exonuclease, DNA polymerase and DNA ligase.
Mutations in repair genes can cause conditions like Xeroderma pigmentosum and colorectal cancer.
Base excision repair mechanisms remove single abnormal bases.
Double-strand breaks are repaired by post-replication repair mechanisms.
Mismatch repair (MMR) corrects mismatched bases during DNA replication.

Types of Mutations

Point Mutation: Single nucleotide change.
- Example: Sickle Cell Anemia - a single base change in the HBB gene leads to a substitution of glutamic acid with valine in hemoglobin.
Insertion Mutation: Addition of one or more nucleotide pairs.
- Example: Huntington’s Disease - insertion of CAG repeats in the HTT gene causes an abnormal huntingtin protein.
Deletion Mutation: Removal of one or more nucleotide pairs.
- Example: Cystic Fibrosis - deletion of three base pairs in the CFTR gene results in a missing phenylalanine, affecting protein function.
Frameshift Mutation: Insertions or deletions that change the reading frame.
- Example: Tay-Sachs Disease - a deletion or insertion in the HEXA gene alters the reading frame, leading to defective enzyme production.
Nonsense Mutation: Point mutation resulting in a premature stop codon.
- Example: Duchenne Muscular Dystrophy - a mutation in the DMD gene introduces a premature stop codon, leading to a truncated dystrophin protein.
Missense Mutation: Substitutes one amino acid for another.
- Example: Sickle Cell Anemia - same as point mutation example.
Silent Mutation: Does not change the amino acid due to redundancy in the genetic code.
Splice Mutation: Alters the nucleotide sequence required for splicing.
- Example: Some forms of β-thalassemia, Gaucher disease, Marfan syndrome.
Dominant-negative Mutation: Produces a nonfunctional protein that impairs the function of the normal protein.
- Example: Mutant p53 protein binds DNA and prevents the attachment of the functional p53 protein.

Chromosomal Mutations

Chromosomal Aberrations: Changes in the structure or number of chromosomes.
- Unbalanced Translocations: Result in chromosomal imbalance and can cause disorders like Patau syndrome.
- Robertsonian Translocation: Can lead to Down Syndrome, often involving chromosomes 14 and 21.
Numerical Mutations: Changes in the number of chromosomes.
- Trisomy 21 (Down Syndrome): Extra copy of chromosome 21.
- Turner Syndrome (Monosomy X): Only one X chromosome in females.
- Klinefelter Syndrome (XXY): Males with an extra X chromosome.
Uniparental Disomy: Inheritance of both copies of a chromosome from one parent.
- Prader-Willi Syndrome: Occurs when both copies of chromosome 15 are inherited from the mother.

Causes of Chromosomal Mutations

Errors in meiosis (non-disjunction).
Exposure to mutagens (radiation, chemicals).
Inherited mutations in germ cells.

Detection of Chromosomal Mutations

Karyotyping: Photographing chromosomes to identify abnormalities.
Fluorescent In Situ Hybridization (FISH): Using fluorescent probes to detect specific mutations.

Consequences of Chromosomal Mutations

Developmental disorders like Down Syndrome and Turner Syndrome.
Cancer, such as Chronic Myeloid Leukemia (CML).
Infertility.

Mutations and Mutagenesis

Spontaneous Mutations: Occur naturally through errors in cell division or DNA replication.
Mutagens: Environmental agents that cause mutations.
- Ionizing Radiation: Electromagnetic waves with short wavelengths (x-rays, γ-rays) or high-energy particles (α particles, β particles).
- Chemical Mutagens: Chemicals like mustard gas, formaldehyde, benzene, and some dyes.

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Description

Explore the fascinating mechanisms of DNA repair and the various types of mutations that can occur. This quiz covers key concepts such as endonuclease function, base excision repair, and specific mutation examples like Sickle Cell Anemia and Cystic Fibrosis. Test your understanding of how these processes impact genetic stability and disease.