Pedigree Analysis

• What is the traditional way to study inheritance?

  To construct a family tree indicating the presence or absence of the trait.
• What is a pedigree?

  A family tree that shows the presence or absence of a genetic trait in each member.
• How can analyzing a pedigree help in genetics?

  It may predict how a trait is inherited.
• What does a pedigree chart display?

  A family tree showing members affected by a genetic trait.
• How are unaffected individuals represented in a pedigree chart?

  With transparent shapes.
• What connects offspring in a pedigree chart?

  They are connected by a sibship line.
• What is a proband in a pedigree?

  The first person in a family treated for a genetic disorder.
• What is the male designation for a proband?

  Proposito or propositus.
• What is the female designation for a proband?

  Proposita.
• What does it mean if parents are consanguineous?

  The parents are related, such as being first cousins.
• How are siblings represented in a pedigree chart?

  Connected by a horizontal sibship line.
• What does monozygotic refer to?

  Identical twins.
• How are monozygotic twins represented in a pedigree chart?

  Linked by diagonal lines connected by a horizontal line.
• What does dizygotic refer to?

  Fraternal twins.
• How are dizygotic twins represented in a pedigree chart?

  Same as monozygotic but lacks a connecting line.
• What does it mean if a trait is autosomal?

  Both males and females can be equally affected or inherit the gene.
• What does it mean if a trait is X-linked?

  X chromosomes will be affected.
• What does it mean if a trait is Y-linked?

  Only males will be affected.
• What are the characteristics of an autosomal dominant trait?

  Both males and females can be affected, and dominant alleles are affected.
• What are the genotypes for an autosomal dominant trait?

  AA = affected, Aa = affected, aa = unaffected.
• What can be inferred if both parents are unaffected in an autosomal dominant trait?

  They cannot both be unaffected if there are affected offspring.
• What is true about autosomal recessive traits?

  Recessive alleles are affected, and heterozygous alleles normally skip generations.
• What are the genotypes for an autosomal recessive trait?

  AA = unaffected, aa = affected, Aa = carrier.
• What can be inferred if both parents are unaffected in an autosomal recessive trait?

  They must be heterozygous carriers.
• What are the characteristics of an X-linked dominant trait?

  Females are affected, and affected males can have affected daughters.
• What are the genotypes for an X-linked dominant trait in females?

  XRXR = affected, XRXr = affected, XrXr = unaffected.
• What are the genotypes for an X-linked dominant trait in males?

  XRY = affected, XrY = unaffected.
• What happens if only the male parent is affected in an X-linked dominant trait?

  There will be 100% affected daughters and normal sons.
• What are the characteristics of an X-linked recessive trait?

  Males are more frequently affected, and affected males often present in each generation.
• What are the genotypes for an X-linked recessive trait in females?

  XRXR = unaffected, XRXr = carrier, XrXr = affected.
• What are the genotypes for an X-linked recessive trait in males?

  XRY = unaffected, XrY = affected.
• What happens if only the female parent is affected in an X-linked recessive trait?

  There will be 100% affected sons and carrier daughters.
• What are the characteristics of a Y-linked trait?

  Only males are affected, and affected fathers will always have affected sons.
• What are the inheritance patterns and characteristics of different genetic traits?

  • **Autosomal Dominant**: Affected person usually has an affected parent; occurs in every generation.
  • **Autosomal Recessive**: Both parents are carriers; not typically seen in every generation.
  • **X-linked Dominant**: Females are more frequently affected; affected males can have affected daughters.
  • **X-linked Recessive**: Males are more frequently affected; affected males often present in each generation.
  • **Y-linked Trait**: Males are affected; affected fathers will always have affected sons.
• What is the OMIM database and its significance?

  • Catalogues human genes in genetic disorders inherited in Mendelian manner.
  • Daily updated version of "Mendelian Inheritance in Man" by Dr. Victor McKusick.
  • First digit indicates inheritance type:
  • 1: Autosomal dominant
  • 2: Autosomal recessive
  • 3: X-linked
  • 4: Y-linked
  • 5: Mitochondrial
  • 6: Autosomal (after May 15, 1994).
• What are some examples of genetic disorders and their OMIM numbers?

  • Achondroplasia: 100800
  • Brachydactyly: 112500
  • Camptodactyly: 114200
  • Crouzon syndrome: 123500
  • Ehlers-Danlos syndrome: 130000
  • Familial hypercholesterolemia: 144010
  • Huntington disease: 143100
  • Cystic fibrosis: 219700
• What are the phenotypes associated with various genetic disorders?

  • **Achondroplasia**: Dwarfism associated with defects in growth regions of long bones.
  • **Brachydactyly**: Malformed hands with shortened fingers.
  • **Cystic fibrosis**: Mucous production that blocks ducts of certain glands, often fatal by early adulthood.
  • **Sickle cell anemia**: Abnormal hemoglobin, blood vessel blockage; early death.
• What are the implications of genetic disorders on health?

  • Genetic disorders can lead to:
  • Progressive degeneration of the nervous system (e.g., Huntington disease).
  • Connective tissue defects (e.g., Marfan syndrome).
  • Increased cancer rates (e.g., Bloom syndrome).
  • Heart defects and high leukemia rates (e.g., Fanconi anemia).