Genetic Diseases and Mendelian Disorders
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Genetic Diseases and Mendelian Disorders

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Questions and Answers

What effect do deletions or insertions of base pairs have when the number involved is not a multiple of 3?

  • The reading frame remains intact.
  • An abnormal protein is synthesized. (correct)
  • The protein synthesis process is enhanced.
  • Translation is not affected at all.

    • Which mutation type is characterized by the amplification of a sequence of three nucleotides?

  • Trinucleotide-repeat mutations (correct)
  • Point mutations
  • Translocations
  • Deletions

    • What is the primary function of noncoding RNAs (ncRNAs)?

  • They enhance protein synthesis directly.
  • They promote mutations in mRNA.
  • They serve important regulatory functions. (correct)
  • They encode proteins for cellular functions.

    • What specific genetic alteration is involved in Chronic Myeloid Leukemia?

    <p>Translocation t(9;22) between BCR and ABL genes.</p> Signup and view all the answers

    What happens to mRNA transcripts when pathogenic structural alterations interfere?

    <p>They fail to form mature mRNA.</p> Signup and view all the answers

    What is often contained within the genetic structure of cancers?

    <p>Somatically acquired structural alterations.</p> Signup and view all the answers

    Which condition involves 250 to 4000 tandem repeats of the sequence CGG?

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

    If an insertion mutation results in three additional base pairs, what is the expected outcome?

    <p>Translation will proceed unaffected.</p> Signup and view all the answers

    What is likely responsible for the tall stature and long legs typical of the syndrome?

    <p>An extra copy of a growth-related gene</p> Signup and view all the answers

    What metabolic syndrome issue is commonly associated with the syndrome described?

    <p>Type 2 Diabetes Mellitus</p> Signup and view all the answers

    Which congenital heart disease has a prevalence of 50% in adults with the syndrome?

    <p>Mitral Valve Prolapse</p> Signup and view all the answers

    What condition has a 20-30 fold higher risk of occurrence in individuals with this syndrome?

    <p>Extragonadal germ cell tumors</p> Signup and view all the answers

    How does the number of CAG repeats in the androgen receptor gene affect sensitivity to androgens?

    <p>Shorter CAG repeats increase sensitivity</p> Signup and view all the answers

    Which of the following bones is NOT affected by the increased incidence of osteoporosis in the syndrome?

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

    What genetic feature is responsible for the preferential inactivation of the shortest CAG repeat allele in the syndrome?

    <p>Presence of an extra X chromosome</p> Signup and view all the answers

    Which autoimmune disease is mentioned as having a higher prevalence in this syndrome?

    <p>Systemic Lupus Erythematosus</p> Signup and view all the answers

    What does incomplete penetrance imply?

    <p>Some individuals carry the mutant gene but are phenotypically normal.</p> Signup and view all the answers

    What is a chain termination mutation?

    <p>A mutation that creates a stop codon within an exon.</p> Signup and view all the answers

    What is variable expressivity?

    <p>The trait's expression can vary significantly among individuals.</p> Signup and view all the answers

    How are most mutations in autosomal genes expressed in heterozygotes?

    <p>They produce partial expression of the mutant allele.</p> Signup and view all the answers

    What percentage of mutations are considered familial?

    <p>80 – 85%</p> Signup and view all the answers

    What contributes to the phenotypic variations in individuals with sickle cell anemia?

    <p>The genotype at the a-globin locus.</p> Signup and view all the answers

    What is primarily affected by mutations involving introns or splice junctions?

    <p>mRNA processing.</p> Signup and view all the answers

    How does the presence of other genes influence mutant allele expression?

    <p>They modify the expression of the mutant allele.</p> Signup and view all the answers

    What is the primary defect associated with Marfan Syndrome?

    <p>Defect in Fibrillin-1</p> Signup and view all the answers

    Which syndrome is characterized by inherited predisposition to aortic aneurysm and cardiovascular manifestations?

    <p>Marfan Syndrome</p> Signup and view all the answers

    What is the effect of Angiotensin Receptor II blockers in mouse models of Marfan Syndrome?

    <p>Reduce aortic root diameter</p> Signup and view all the answers

    What type of inheritance pattern is associated with Marfan Syndrome?

    <p>Autosomal Dominant</p> Signup and view all the answers

    Which protein is a major component of microfibrils in the extracellular matrix?

    <p>Fibrillin-2</p> Signup and view all the answers

    G6PD deficiency can lead to which condition when exposed to certain drugs?

    <p>Severe hemolytic anemia</p> Signup and view all the answers

    What is a common clinical feature of Ehlers-Danlos Syndromes?

    <p>Joint hypermobility</p> Signup and view all the answers

    What does the defect in dystrophin primarily affect?

    <p>Skeletal muscles</p> Signup and view all the answers

    How is Familial Hypercholesterolemia primarily characterized?

    <p>Defect in receptors for LDL</p> Signup and view all the answers

    Which of the following is a characteristic abnormality observed in Marfan Syndrome?

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

    What is the incidence rate of Klinefelter Syndrome in live male births?

    <p>1 in 660</p> Signup and view all the answers

    What primary factors contribute to the clinical features of Klinefelter Syndrome?

    <p>Aneuploidy and increased gene dosage</p> Signup and view all the answers

    What characteristic body habitus is commonly associated with Klinefelter Syndrome?

    <p>Eunuchoid body habitus</p> Signup and view all the answers

    What percentage of X-linked genes escape X-inactivation in Klinefelter Syndrome?

    <p>35%</p> Signup and view all the answers

    Which of the following is a common feature of Klinefelter Syndrome?

    <p>Small testicular size</p> Signup and view all the answers

    Which gene is mentioned as not subject to X-inactivation and can affect somatic features in Klinefelter Syndrome?

    <p>SHOX gene</p> Signup and view all the answers

    What is a possible consequence of the presence of supernumerary X chromosomes in patients with Klinefelter Syndrome?

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

    Which of the following cognitive abilities is commonly affected in patients with Klinefelter Syndrome?

    <p>Verbal skills</p> Signup and view all the answers

    Study Notes

    Genetic Diseases

    • mRNA Processing: Mutations can interfere with normal mRNA processing, leading to failure in forming mature mRNA and blocking translation.
    • Deletions/Insertions: These can alter the reading frame, resulting in an abnormal protein with either missing or additional amino acids.
    • Point Mutations: These can occur in promoter sequences, affecting mRNA processing.
    • Nonsense Mutations: These create a stop codon in an exon, triggering premature protein termination.
    • Trinucleotide-Repeat Mutations: These involve amplifications of three nucleotide sequences, as seen in Fragile X Syndrome, characterized by an expansion of CGG repeats in the FMR1 gene.

    Mendelian Disorders

    • Individuals carry several deleterious recessive genes, which usually remain unexpressed.
    • 80-85% of these mutations are familial, while 15-20% are new mutations acquired de novo.
    • Most mutations in autosomal genes exhibit partial expression in heterozygotes and full expression in homozygotes.
    • Incomplete Penetrance: Individuals inherit the mutant gene but don't express the trait.
    • Variable Expressivity: The trait is expressed differently among individuals with the same gene mutation.

    Disorders associated with Defects in Structural Proteins

    • These affect the connective tissue (CT) and involve multiple organs.
    • Marfan Syndrome:
      • A CT disorder affecting the skeleton, eyes, and cardiovascular system.
      • Predominantly inherited via autosomal dominant mode.
      • Caused by mutations in the fibrillin-1 gene (FBN1).
      • Fibrillin-1 is a major component of microfibrils in the extracellular matrix (ECM).
      • Defective fibrillin-1 disrupts microfibril formation, leading to Marfan Syndrome.
    • Ehlers-Danlos Syndromes (EDS): These are a group of genetic disorders affecting collagen synthesis and structure, causing various connective tissue problems.

    Disorders associated with Defects in Receptor Proteins

    • Familial Hypercholesterolemia:
      • One of the most frequent genetic diseases involving sex chromosomes and a common cause of hypogonadism in males.
      • Results from mutations in the gene encoding the LDL receptor, leading to elevated cholesterol levels.

    Klinefelter syndrome

    • Clinical Features: Individuals with Klinefelter syndrome have an extra X chromosome (XXY).
    • Pathogenic Mechanism:
      • Uneven dosage compensation: 35% of X-linked genes escape inactivation, resulting in an extra dose of these genes compared to normal males.
      • Overexpression of certain X-linked genes, including those involved in growth, contributes to hypogonadism and the distinctive body habitus.
      • Preferential inactivation of the X chromosome carrying the androgen receptor allele with the shortest CAG repeat, leading to reduced androgen sensitivity.

    Pharmacogenetics

    • G6PD deficiency:
      • Individuals with G6PD deficiency are usually asymptomatic, but can develop severe hemolytic anemia upon exposure to certain drugs like primaquine.

    Genetically Determined Adverse Reactions to Drugs

    • Enzyme deficiencies can be unmasked upon exposure to specific drugs, leading to adverse reactions.

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    Genetic Disorders PDF

    Description

    Test your knowledge on genetic diseases and Mendelian disorders. This quiz covers key concepts such as mRNA processing, various mutations, and the inheritance patterns of genetic disorders. Understand the implications of different types of mutations and how they influence genetic traits.

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