Genetic Diseases Overview
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Genetic Diseases Overview

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Questions and Answers

What defines a hereditary disease?

  • A condition that is present at birth and does not have a genetic basis
  • A disease transmitted through the germline that has a genetic basis (correct)
  • A condition that can be caused by somatic mutations
  • A defect that arises from environmental factors only

    • Which of the following is a characteristic of chromosomal disorders?

  • They are solely inherited in an autosomal recessive pattern
  • They only affect autosomes, not sex chromosomes
  • They involve structural or numerical alterations in chromosomes (correct)
  • They are always caused by environmental factors

    • Which term describes a condition that is present at birth but is not necessarily genetic?

  • Hereditary
  • Acquired
  • Familial
  • Congenital (correct)

    • What type of genetic disorder is associated with interactions between multiple genes and environmental factors?

    <p>Complex multigenic disorders</p> Signup and view all the answers

    What is the typical outcome of mutations affecting germ cells?

    <p>They can result in inherited diseases</p> Signup and view all the answers

    How are disorders caused by mutations in single genes characterized?

    <p>They are highly penetrant and cause significant disease</p> Signup and view all the answers

    Which of the following diseases is an example of a complex multigenic disorder?

    <p>Hypertension</p> Signup and view all the answers

    Which of the following statements is true regarding congenital conditions?

    <p>They can arise from infections like congenital syphilis</p> Signup and view all the answers

    What typically allows women to remain healthy in the presence of a mutated gene on one X-chromosome?

    <p>Women have two X-chromosomes, allowing for a working version.</p> Signup and view all the answers

    Which of the following is classified as an X-linked recessive disorder?

    <p>Fragile X syndrome</p> Signup and view all the answers

    What happens to the repeat number at a locus in the FMR1 gene when it exceeds a specific threshold?

    <p>It creates a full mutation.</p> Signup and view all the answers

    What is a characteristic feature of familial cases of Fragile X syndrome in males?

    <p>They typically present with moderate to severe mental retardation.</p> Signup and view all the answers

    In cases of maternal inheritance of mitochondrial disorders, what is the genetic outcome for children of affected mothers?

    <p>100% of children are affected.</p> Signup and view all the answers

    Which description accurately defines aneuploidy?

    <p>Not a multiple of the haploid number.</p> Signup and view all the answers

    What describes a euploid chromosome condition?

    <p>A multiple of the haploid number.</p> Signup and view all the answers

    Which chromosomal abnormality is common in first-trimester aborted fetuses?

    <p>Aneuploidy.</p> Signup and view all the answers

    Which of the following statements is true about autosomal dominant disorders?

    <p>One copy of the mutant allele can result in disease manifestation.</p> Signup and view all the answers

    What is a characteristic of autosomal recessive disorders?

    <p>They require two copies of the mutant allele to show disease.</p> Signup and view all the answers

    Which of the following is NOT typically classified as an autosomal dominant disorder?

    <p>Cystic Fibrosis</p> Signup and view all the answers

    How is Marfan's syndrome caused?

    <p>By a defect in fibillin.</p> Signup and view all the answers

    Which outcome is likely for a child if one parent has an autosomal dominant disorder?

    <p>The child has a 50% chance of being affected.</p> Signup and view all the answers

    Most autosomal recessive disorders are primarily caused by?

    <p>A defect in an enzyme in a metabolic pathway.</p> Signup and view all the answers

    In the inheritance pattern of autosomal dominant disorders, which of the following is true?

    <p>Both genders can exhibit symptoms and can transmit the condition.</p> Signup and view all the answers

    What is the chromosomal composition for Turner syndrome?

    <p>45, X0</p> Signup and view all the answers

    Which of the following statements about chromosomal abnormalities is true?

    <p>Most chromosomal abnormalities are de novo mutations.</p> Signup and view all the answers

    What genetic condition is typically associated with a karyotype of 47, XX, +21?

    <p>Down syndrome</p> Signup and view all the answers

    What is a common consequence of chromosomal abnormalities during early pregnancy?

    <p>Greater likelihood of fetal spontaneous abortion</p> Signup and view all the answers

    Which feature is NOT commonly associated with Turner syndrome?

    <p>Increased height</p> Signup and view all the answers

    Which structural chromosomal abnormality involves the loss of one arm of a chromosome?

    <p>Isochromosome</p> Signup and view all the answers

    Fluorescence in situ hybridization (FISH) is best described as a technique that uses what?

    <p>DNA probes to identify specific chromosomal regions</p> Signup and view all the answers

    What is the most common cause of Down syndrome?

    <p>Trisomy 21</p> Signup and view all the answers

    What is a point mutation?

    <p>Change in a single base of DNA to a different base</p> Signup and view all the answers

    Which of the following best describes a frameshift mutation?

    <p>It involves a deletion or insertion of nucleotides.</p> Signup and view all the answers

    What distinguishes a trinucleotide repeat disorder from other mutations?

    <p>It is characterized by the amplification of sets of three nucleotides.</p> Signup and view all the answers

    In sickle cell disease, what is the specific change that occurs in the hemoglobin structure due to point mutation?

    <p>Amino acid glutamate is replaced with valine.</p> Signup and view all the answers

    What occurs when the repeat number of a trinucleotide sequence exceeds a certain threshold?

    <p>The allele is considered a full mutation.</p> Signup and view all the answers

    Which mutation type is characterized by the addition of nucleotides?

    <p>Frameshift mutation</p> Signup and view all the answers

    In the context of single gene defects, what is a common characteristic of a deletion mutation?

    <p>It results in the loss of one or more nucleotides.</p> Signup and view all the answers

    What is a premutation in the context of trinucleotide repeat disorders?

    <p>It occurs before a full mutation, maintaining stability.</p> Signup and view all the answers

    Study Notes

    Genetic Diseases Overview

    • Genetic aspects are implicated in nearly all diseases, including hypertension, diabetes, and cancer susceptibility.
    • High rates of miscarriages are associated with fetal chromosomal abnormalities.
    • The Human Genome Project has sequenced around 30,000 genes.

    Definitions

    • Congenital Conditions: Defects present at birth, not necessarily genetic (e.g., congenital syphilis).
    • Hereditary Conditions: Genetic disorders passed down from parents through germline cells.

    Classification of Genetic Disorders

    • Single Gene Disorders: Caused by mutations in single genes, often with significant phenotypic effects.
    • Chromosomal Disorders: Result from structural or numerical alterations of chromosomes.
    • Complex Multigenic Disorders: Caused by multiple gene variants and environmental interactions (e.g., diabetes, hypertension).

    Single Gene Mutations

    • Point Mutations: Substitution of a single base pair in DNA.
    • Frameshift Mutations: Caused by insertions or deletions of nucleotides, altering the subsequent reading frame.
    • Trinucleotide Repeat Disorders: Involves expansion of a repeat sequence beyond a stable threshold, leading to instability in the allele.

    Mendelian Transmission Patterns

    • Follow Mendelian inheritance rules: autosomal dominant, autosomal recessive, and X-linked disorders.

    Autosomal Dominant Disorders

    • Manifest in heterozygous individuals; one mutant allele (D) from an affected parent can cause the disease.
    • Common disorders include Huntington’s disease, Neurofibromatosis, and Ehlers-Danlos syndrome.

    Autosomal Recessive Disorders

    • Requires mutations in both copies of a gene; examples include cystic fibrosis and phenylketonuria.
    • Majority are metabolic disorders, often linked to enzyme deficiencies.

    X-Linked Recessive Disorders

    • Predominantly affect males, who have only one X chromosome; conditions include Duchenne muscular dystrophy and hemophilia.
    • Women can be carriers without showing symptoms due to the presence of a second X chromosome.

    Fragile X Syndrome

    • An X-linked disorder often leading to mental retardation, characterized by specific physical features.
    • Caused by CGG trinucleotide repeat expansion in the FMR1 gene.

    Mitochondrial Disorders

    • Inherited solely from the mother; all children of affected mothers will have the disorder, while those of affected fathers will not.

    Chromosomal Abnormalities

    • Common abnormalities include numerical (e.g., trisomy, monosomy) and structural alterations (e.g., deletions, translocations).
    • Found in 1 in 200 live births; significant in first-trimester abortions.

    Examples of Chromosomal Conditions

    • Down Syndrome: Caused primarily by Trisomy 21, associated with mental retardation and characteristic physical features.
    • Turner Syndrome: Monosomy X (45,X), leading to short stature and infertility, commonly resulting in fetal loss.

    Diagnosis Techniques

    • Karyotyping: Provides a global view of chromosome structure and number but offers low resolution.
    • Fluorescence In Situ Hybridization (FISH): Utilizes DNA probes for targeted chromosomal analysis, allowing for more specific genetic diagnostics.

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    Genetic Diseases PDF

    Description

    This quiz explores the definitions and classifications of genetic diseases, including congenital and hereditary conditions. Participants will learn about Mendelian inheritance patterns, risk factors, and the significance of chromosomal analysis in understanding genetic disorders.

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