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Inherited Diseases
Autosomal Recessive and
Autosomal Dominant
Patterns of Inheritance
Autosomal Recessive
Is caused by a recessive allele bb.
Relatively Rare
Common in ethnic groups
Cystic Fibrosis
Most common among white Americans
Approximately 1 and 20 white Americans
are carriers.
1 in 2000 babies are born with CF
It is due to a defective protein in the
plasma membrane, it results in the
formation & accumulation of thick mucus
in the lungs and digestive tract.
Tay-Sachs
Affects the Central Nervous System
Results in the absence of an enzyme that
breaks down lipids in the CNS.
Common in Amish, and Ashkenzic Jews.
Babies only live to around the age 5
1 in 27 babies are born with the disease.
PKU- Phenylketonuria
Results in the absence of enzyme that
converts phenylalanine into tryosine.
Therefore it accumulates in the body and
results in damage to the CNS.
Most common in Sweden and Norway.
Causes mental retardation.
Can be controlled by removing foods that
contain phenylalanine in their diets.
Autosomal Dominance
Results from a dominant allele. Therefore,
if the individual has at least 1 allele, the
trait will be present.
Most dominant diseases are rare.
Huntington’s Disease
Results in the breakdown of certain areas
of the brain.
Lethal
onset is around age 30-50
normally pass down allele before they
realize they have the trait.
Simple Dominant Traits
Tongue Rolling
Hapsburg lip (large
lower lip)
Hanging earlobes
hitchhiker’s thumb
almond shaped eyes
thick lips
long eye lashes
Presence of hair in
middle section of the
fingers
close set eyes
(distance between
the eyes)
Hair texture (curly is
dominant)
Polydactyl- 6 fingers.
Rare but dominant.