Exam 2 Tables.docx - Pedigree Illustrating the Inheritance Pattern of Postaxial Polydactyly an Autosomal Dominant Disorder Affected individuals are

Exam 2 Tables.docx - Pedigree Illustrating the Inheritance...

This preview shows page 2 - 4 out of 9 pages.

Pedigree Illustrating the Inheritance Pattern of Postaxial Polydactyly, an AutosomalDominant Disorder. Affected individuals are represented by shading.TABLE 2-1Characteristics of Various Chromosome DisordersDisease/DisorderFeaturesDown SyndromeTrisomy of Chromosome 21IQUsually ranges from 20 to 70 (intellectual disability)Male/female findingsVirtually all males are sterile; some females can reproduceFaceDistinctive: low nasal bridge, epicanthal folds, protruding tongue, low-set earsMusculoskeletal systemPoor muscle tone (hypotonia), short statureSystemic disordersCongenital heart disease (one third to half of cases), reduced ability to fight respiratory tract infections, increased susceptibility to leukemia—overall reduced survival rate; by age 40 years usually develop symptoms similar to those of Alzheimer diseaseMortalityAbout 75% of fetuses with Down syndrome abort spontaneously or are stillborn; 20% of infants die before age 10 years; those who live beyond 10 years have life expectancy of about 60 yearsCausative factors97% caused by nondisjunction during formation of one of parent's gametes or during early embryonic development; 3% result from translocations; in 95% of cases,
Background image
Disease/DisorderFeaturesnondisjunction occurs when mother's egg cell is formed; remainder involve paternal nondisjunction; 1% are mosaics—these have a large number of normal cells, and effects of trisomic cells are attenuated and symptoms are generally less severeTurner Syndrome(45,X) Monosomy of X ChromosomeIQNot considered to be intellectually disabled, although some impairment of spatial and mathematical reasoning ability is foundMale/female findingsFound only in femalesMusculoskeletal systemShort stature common, characteristic webbing of neck, widely spaced nipples, reduced carrying angle at elbowSystemic disordersCoarctation (narrowing) of aorta, edema of feet in newborns, usually sterile and have gonadal streaks rather than ovaries; streaks are sometimes susceptible to cancerMortalityAbout 15-20% of spontaneous abortions with chromosome abnormalities have this karyotype, most common single-chromosome aberration; highly lethal during gestation, only about 0.5% of these conceptions survive to termCausative factors75% inherit X chromosome from mother, thus caused by meiotic error in father; frequency
Background image
Image of page 4

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture