Lecture 20
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Questions and Answers

What is the probability that a male child of a heterozygous carrier mother will be affected?

  • 75%
  • 100%
  • 50% (correct)
  • 25%

    • What is the probability that a female child of a heterozygous carrier mother will be a carrier?

  • 50% (correct)
  • 25%
  • 75%
  • 100%

    • What is the probability that a female child of a heterozygous carrier mother will be unaffected?

  • 50% (correct)
  • 25%
  • 75%
  • 100%

    • What is the probability that a carrier female will have an affected male child?

    <p>50%</p> Signup and view all the answers

    What is the probability that a carrier female will have an affected female child?

    <p>0%</p> Signup and view all the answers

    What is the genotype of an affected male child?

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

    What type of inheritance pattern is described in the text where the phenotype is expressed when only one gene copy has a pathogenic variant?

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

    Where is the chromosomal location of the gene locus in X-linked dominant inheritance?

    <p>Sex chromosomes (X and Y chromosomes)</p> Signup and view all the answers

    What is the genotype of a female who is homozygous for the mutant allele?

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

    What is the result of allele segregation in X-linked dominant inheritance?

    <p>The two alleles for each gene are separated into two different gamete cells</p> Signup and view all the answers

    What is the phenotype of a male who inherits an X-linked dominant allele?

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

    What is the difference between a heterozygous female and a homozygous female in X-linked dominant inheritance?

    <p>Heterozygous females have one mutant allele, while homozygous females have two mutant alleles</p> Signup and view all the answers

    What is the characteristic of X-linked dominant inheritance?

    <p>All female offspring of an affected male are affected</p> Signup and view all the answers

    What is the gene responsible for Rett Syndrome?

    <p>MECP2</p> Signup and view all the answers

    What is a common finding in Rett Syndrome?

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

    What is the definition of a recessive allele?

    <p>An allele that is expressed only when the two gene copies have the pathogenic variant</p> Signup and view all the answers

    What is the pattern of inheritance in X-linked recessive inheritance?

    <p>Homozygous female is affected, while heterozygous female is a carrier</p> Signup and view all the answers

    Why is Rett Syndrome inherited as an X-linked dominant disease?

    <p>Because the gene is located on the X chromosome</p> Signup and view all the answers

    What is the characteristic of vertical transmission?

    <p>Transmission from parent to offspring</p> Signup and view all the answers

    What determines the pattern of inheritance of a disease?

    <p>The chromosomal location of the gene locus</p> Signup and view all the answers

    What is the type of inheritance associated with red and green color perception defects?

    <p>X-linked recessive</p> Signup and view all the answers

    What is the function of opsins in cone cells?

    <p>To react to the wavelength of the three main colors</p> Signup and view all the answers

    What is the purpose of the OMIM database?

    <p>To catalog information on genetic disorders and traits</p> Signup and view all the answers

    What is the name of the database created by Dr. Victor McKusick?

    <p>Online Mendelian Inheritance in Man</p> Signup and view all the answers

    What is the name of the test that can diagnose red-green colorblindness?

    <p>Colormax test</p> Signup and view all the answers

    What is the OMIM code for Green Colorblindness?

    <p>OMIM 303800</p> Signup and view all the answers

    What is the purpose of cone cells in the retina?

    <p>To react to the wavelength of light</p> Signup and view all the answers

    What is the name of the school of medicine that maintains the OMIM database?

    <p>Johns Hopkins University School of Medicine</p> Signup and view all the answers

    What criteria are entries in the OMIM database indexed and searchable by?

    <p>Gene name, disease name, phenotype, and inheritance pattern</p> Signup and view all the answers

    What is the purpose of OMIM numbers in the OMIM database?

    <p>To identify genetic disorders and traits</p> Signup and view all the answers

    What is the function of mitochondria in cellular respiration?

    <p>Energy production and ATP</p> Signup and view all the answers

    What is the characteristic of mitochondrial DNA in each cell?

    <p>It is polyploid</p> Signup and view all the answers

    What happens to the mitochondria from the sperm during fertilization?

    <p>They are degraded after fertilization</p> Signup and view all the answers

    What is the source of mitochondrial DNA in the zygote?

    <p>Only ovum</p> Signup and view all the answers

    What is the significance of mitochondrial inheritance?

    <p>It affects only the maternal lineage</p> Signup and view all the answers

    What is the result of defects in mitochondrial respiration and energy production?

    <p>Severe disease</p> Signup and view all the answers

    Study Notes

    X-Linked Dominant (XLD)

    • XLD is a pattern of inheritance where a mutant allele on the X chromosome is enough to express the phenotype.
    • Both homozygous and heterozygous females are affected, while males are hemizygous (only one X chromosome).
    • Affected individuals have at least one affected parent, and there is no male-to-male transmission.
    • All female offspring of an affected male are affected.
    • Clinical application: Rett Syndrome (OMIM 312750) is an X-linked dominant disease caused by a mutation in the MECP2 gene, essential for brain development.

    X-Linked Recessive (XLR)

    • XLR is a pattern of inheritance where a mutant allele on the X chromosome is only expressed when there are two copies of the allele.
    • Homozygous females are affected, while heterozygous females are carriers.
    • Clinical application: Green Colorblindness (OMIM 303800) and Red Colorblindness (OMIM 303900) are X-linked recessive disorders due to mutations in visual pigment genes or receptors in the retina.

    X-Linked Recessive (XLR) Inheritance Patterns

    • A carrier female has a 50% chance of having an affected male child and 0% chance of having an affected female child.
    • For a heterozygous carrier mother, there are three possible outcomes for each child: 50% healthy, 50% healthy carrier (female), and 50% affected (male).

    OMIM Database

    • OMIM stands for Online Mendelian Inheritance in Man, created in 1966 by Dr. Victor McKusick.
    • It is a comprehensive, publicly available database of human genes, genetic disorders, and traits.
    • Each entry includes a detailed description of the gene, its functions, and the associated genetic disorder or trait, and mode of inheritance.
    • OMIM numbers are unique identifiers assigned to each entry, used to identify and study genetic disorders and traits.

    Mitochondrial Inheritance

    • Mitochondria are cytoplasmic organelles responsible for cellular respiration and energy production.
    • Each cell contains multiple copies of mitochondrial DNA (mtDNA), which is essential for normal cell function.
    • Defects in mitochondrial DNA can result in severe disease.
    • Mitochondrial DNA is inherited solely from the mother, as paternal mitochondria are degraded after fertilization.

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    Related Documents

    X-linked Dominant (XLD) Lecture PDF

    Description

    This quiz is about understanding the X-linked dominant inheritance pattern, including the location of the gene, genotype, and phenotype. It involves the study of X-linked dominant traits and their expression.

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