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Mendelian Pedigree patterns Autosomal dominant Autosomal recessive X-Linked recessive X-linked dominant Y-linked

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  • Mendelian Pedigree patternsAutosomal dominantAutosomal recessiveX-Linked recessiveX-linked dominantY-linked

  • Autosomal dominant (3.2A)Marfans syndrome, Neurofibromatosis, Huntington Disease, RetinoblastomaAn affected person usually has at least one affected parent.Affects either sex.Transmitted by either sex.A child of affected x unaffected mating has a 50% chance of being affected.

  • Autosomal recessive (3.2B)Cystic fibrosis, Phenylketonuria, Tay-SachsAffected people are usually born to unaffected parents.Parents of affected people usually asymptomatic carriers.There is an increased incidence of parental consanguinity.Affects either sex.After birth of an affected child each subsequent child has 25% chance of being affected.

  • X-linked recessive (3.2C)Hemophilia, Lesch-NyhanAffects mainly males.Affected males are usually born to unaffected parents; the mother is typically an asymptomatic carrier and may have affected male relatives.Females may be affected if father is affected and mother is a carrier.No male to male transmission.

  • X-linked dominant (3.2D)Vitamin D resistant rickets.Affects either sex, but more females than males.Females are often more mildly and more variably affected than males.The child of an affected female, regardless of sex, has a 50% chance of being affected.For an affected male, all daughters and no sons are affected.

  • Y-linked inheritance (3.2E)Affects only males.Affected males always have an affected father unless there is a new mutation.All sons of an affected man are affected.

  • Mitochondrial diseasesTypical pattern for hearing loss.Atypical Lebers hereditary optic atrophy.

  • Complications to basic pedigreesTypical pattern for blood group O (3.13).AD with nonpenetrance in II2 (3.14).AD with variable expression (3.17).Genetic imprinting (3.18).X-linked dominant incontinentia pigmenti (3.19).X-linked recessive with inbreeding (3.20).A new AD mutation, mimicking recessive (3.21).

  • Complications to basic pedigreesTypical pattern for blood group O (3.13).Appears as a dominant pattern

  • Complications to basic pedigreesAD with nonpenetrance in II2 (3.14).

  • Complications to basic pedigreesAD with variable expression (3.17).Waardenburg syndromeShading 1st quad = hearing lossShading of 2nd quad = different colored eyesShading of 3rd quad = white forelockShading of 4th quad = premature graying of hair

  • Complications to basic pedigreesGenetic imprinting (3.18).AD glomus tumors manifest only when gene s inherited from father (A).

    AD Beckwith-Wiedemann syndrome manifests only when gene is inherited from mother (B).

  • Complications to basic pedigreesX-linked dominant incontinentia pigmenti (3.19).Affected males abort spontaneously.

  • Complications to basic pedigreesX-linked recessive with inbreeding (3.20).Inbreeding gives an affected female and apparent male to male transmission.

  • Complications to basic pedigreesA new AD mutation, mimicking recessive (3.21).

  • Huntington Age of OnsetProbability that an individual carrying the disease gene will have developed symptoms by a given age (A).Risk that a healthy child of an affected parent carries the disease gene at a given age (B).

  • New Mutation in X-linked recessive DMDIII1 has the grandparental X which acquired a mutation at some point.III1 caries a new mutationII1 is a germinal mosaic (risk for children, but not sisters)II1 was the result of a single mutation, standard recurrence risk or X-linked recessives, sister free of risk.I1 was a germinal mosaic, all the sisters have a significant risk, which is hard to quantify.

  • Germinal MosaicAD adenomatous polyposisNormal = bottom band, mutant = upper bandsFemales II2 and II3 are carriers of high risk allele.High risk chromosome is blue, II2 shows mosaic expression while III4 does not.

  • Hardy-Weinberg Lawp2 + 2pq + q2 = 1.0

    p + q = 1.0

  • IncidenceAutosomal recessiveq2

    Autosomal dominantp2 + 2pq

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