Transcript Human Diseases A Systemic Approach Sixth Edition

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.