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
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Slide 10
Slide 24
Sickle Cells
Down Syndrome
Mulvihill, Zelman, Holdaway, Tompary, and Raymond
Human Diseases: A Systemic Approach, 6e
Copyright ©2006 by Prentice-Hall, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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.
(50% chance for an affected child).
Click on the screenshot to view an animation showing
sickle cells.
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Autosomal Dominant Diseases
Polydactyly
Achondroplasia
Marfan’s syndrome
Familial
hypercholesterolemia
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
Click on the screenshot to view a video on the topic of
Down syndrome.
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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. 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.
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.
