Human Diseases A Systemic Approach Sixth Edition Mary Lou Mulvihill Mark Zelman Paul Holdaway Elaine Tompary Jill Raymond Chapter 5 Heredity and Disease

Chapter 5 Heredity and Disease Slide 10 Sickle Cells Slide 24 Down Syndrome Copyright ©2006 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Mulvihill, Zelman, Holdaway, Tompary, and Raymond Human Diseases: A Systemic Approach, 6e

Heredity DNA – blueprint 46 chromosomes (genes) (alleles) 44 autosomes 2 sex chromosomes: X and Y Karyotype

Genetic Inheritance Alleles Homozygous Heterozygous Dominant Recessive

Figure 5-1: Meiosis.

Figure 5-2: Normal human karyotype. (©Custom Medical Stock Photo.)

Table 5-1: Hereditary Disease Locations

Autosomal Dominant Transmission of a dominant allele 50% chance of being affected Disease appears in every generation Males and females equally being affected

Figure 5-3: Transmission of autosomal dominant disorders Figure 5-3: Transmission of autosomal dominant disorders. (50% chance for an affected child).

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Autosomal Dominant Diseases Polydactyly Achondroplasia Marfan’s syndrome Familial hypercholesterolemia

Figure 5-4: A 12-year old Achondroplastic dwarf Figure 5-4: A 12-year old Achondroplastic dwarf. Note the disproportion of the limbs to the trunk, the curvature of the spine, and the prominent buttocks.

Autosomal Recessive Disease manifests when individual is homozygous for the defective allele Parents are carriers; they do not have the disease Child has a 25% chance of being affected Recessive allele appears more frequently in close intermarriages

Figure 5-5: Transmission of recessive disorders (25% chance for an affected child).

Autosomal Recessive Diseases Phenylketonuria Galactosemia Sickle cell anemia Tay-Sachs disease Albinism

Normal red blood cells. (©Phototake NYC.)

Sickle blood cells. (©Photo Researchers, Inc.)

Figure 5-6: Enzyme block in phenylketonuria (PKU)

Autosomal Recessive Diseases Color blindness: inability to distinguish colors Hemophilia Fragile X syndrome – a break or weakness on long arm of X chromosome

Sex-Linked Inheritance Defective gene on X chromosome Defective X on male is unmasked and the trait is expressed. Female is carrier for the disease; heterozygous Male transmits the defective allele to his daughters.

Figure 5-7: Transmission of sex-linked disorders.

Abnormal Chromosome Diseases Altered number or structure Failure of chromosome to separate during cell division Loss of autosome is usually incompatible with life

Patau Syndrome +13

Down Syndrome Caused by the presence of an extra autosome, nondisjunction Results in mental retardation and shorter life expectancy Characteristic appearance: slanted eyes, extra fold of skin at upper medial corner of the eye, protrusion of the tongue, short nose Short stature, underdeveloped sex organs

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Figure 5-8: Girl with Down syndrome Figure 5-8: Girl with Down syndrome. (©Beebe / Custom Medical Stock Photo.)

Familial Disease Diseases run in families but means of inheritance are not understood Most likely the effects of several genes working together Examples: diabetes, allergies, familial polyposis

Cri Du Chat Syndrome Cat-like cry Caused by deletion of part of the short arm of chromosome 5 Results in an abnormally small head with a deficiency in cerebral brain tissue Widely spaced eyes and mental retardation

Sex Anomalies Turner’s syndrome: missing sex chromosome Klinefelter’s syndrome: extra sex chromosome Hermaphrodite: has both testes and ovaries Pseudohermaphrodite: has either

Figure 5-9: A 21-year-old patient with Turner’s syndrome Figure 5-9: A 21-year-old patient with Turner’s syndrome. The chest is broad and the nipples are small and pale. Pubic hair is totally lacking.

Figure 5-10: A 19-year-old patient with Klinefelter’s syndrome Figure 5-10: A 19-year-old patient with Klinefelter’s syndrome. Extremities are excessively long, pubic hair is scanty, and genitals undeveloped. Body proportions resemble those of a eunuch.

Figure 5-11: A 22-year-old patient with pseudohermaphroditism, reared as a girl because of ambiguous genitalia. Surgery and tissue studies showed the gonads to be testes.