Genetic Disorders

Caused by a harmful mutation (physical change of gene) Mutation originally occurs in gamete and is passed to future generations (inherited) The gene that is mutated determines the disease. The allele that is mutated determines its inheritance pattern

Autosomal Recessive Mutation produces a recessive allele Genotypes: CC: unaffected Cc: carrier (unaffected) cc: affected Examples: Cystic Fibrosis, Tay-Sachs, Sickle Cell Anemia (inc. dominance) If two unaffected parents have a child with cystic fibrosis, what are their genotypes?

Autosomal Recessive Pedigree

X-linked Recessive Mutation produces a recessive allele on the X chromosome. Genotypes: Examples: Hemophilia A, Red-green Color Blindness FemaleMale X H X H - unaffected X H Y - unaffected X H X h – carrier (unaffected) X h Y - affected X h X h - affected No male carrier Diane’s father and brother have hemophilia. There is no family history of hemophilia in Craig’s family. What is the probability that their child will have hemophilia. What if they have a girl? A boy?

X-linked Recessive Pedigree

Autosomal Dominant Mutation produces a dominant allele Genotypes: HH: affected Hh: affected hh: unaffected Examples: Huntington Disease Although Huntington disease is very rare in the total population, it appears at a rate of 50 percent in affected families. Explain this in genetic terms.

Autosomal Dominant Pedigree

Chromosomal Disorders +/- chromosomes 1 extra: trisomy 1 missing: monosomy Caused by nondisjunction: failure of one or more chromosome pairs to separate during meiosis Examples: Down Syndrome, Klinefelter’s Syndrome, Turner’s Syndrome

Nondisjunction can occur during Meiosis I or Meiosis II

Down Syndrome (Trisomy 21)

Turner Syndrome (45, X)

Klinefelter Syndrome (47, XXY)