Some Genetic Disorders
Genetic Disorders
• All of the disorders in this presentation are
autosomal. This means they NOT located on the
sex chromosomes, but on the other chromosomes.
• Dominant (big letters) disorders show up with
just one allele present from one parent.
• Recessive (little letters) disorders only show up
when two alleles are present. Parents don’t have
to have it for a child to have it.
Huntington’s Disease
• Dominant disorder
• Symptoms:
–
–
–
–
–
Breakdown of brain and nerve tissue
Irritability
Loss of coordination and balance
Trouble speaking and swallowing
Death
Huntington’s Disease
Other Important Info.:
• Rare, but lethal
• Symptoms show up
between ages 30 – 50
• Affected individuals may
have already had children
and passed it on to them
before they knew they had
HD.
• Very similar to
Parkinson’s Disease.
Huntington’s Disease
Answer: ______ % chance
Practice Problem:
A man who is
homozygous for HD
and a woman that does
not have HD have a
child. What is the
chance that the child
will have HD?
Achondroplasia (Dwarfism)
• Dominant disorder
• Symptoms:
– Short arms, short legs, but normal sized skull
and torso (Disproportionate dwarfism)
• Other Important Info.:
– Inhibits bone growth- cartilage is slow to turn
to bone
– Have normal intellectual capacity
Achondroplasia (Dwarfism)
“Big World Little People” Family
Achondroplasia (Dwarfism)
Practice Problem:
What is the chance of
2 dwards that are
heterozygous for the
disease to have a
normal-sized child?
Answer: _____% chance
Cystic Fibrosis
• Recessive disorder
• Symptoms:
– Overproduction of/and buildup of mucus in
lungs and digestive tract
– Salty skin (very salty sweat)
– Difficulty breathing
– Chronic coughing and wheezing
– Inflammation of lungs
Cystic Fibrosis
• Other Important Info.:
– Life expectancy: 30 yrs
– Most common genetic
disease in Caucasians
– Treatments: physical
therapy and gene
therapy
Cystic Fibrosis
Answer: _____% chance
• Practice Problem:
A child’s mom is
completely normal.
His dad is a carrier for
CF. What is the
chance that the child
will also be a carrier?
Tay-Sachs Disease
• Recessive disorder
• Symptoms:
–
–
–
–
–
Lipids buildup in central nervous system
Loss of motor skills
Blindness
Paralysis
Death
Tay-Sachs Disease
Other Important Info:
• Life expectancy 5 yrs
• Most common in
Jewish and Amish
people
Tay-Sachs Disease
Practice Problem:
Two carriers for TaySachs have a child.
What is the chance
that the child will have
Tay-Sachs?
Answer: _____% chance
Phenylketonuria (PKU)
• Recessive disorder
• Symptoms:
– Phenlyalanine (an amino
acid) builds up in body
– Damages central nervous
system
• Causes mental retardation,
seizures, tremors,
social/behavior problems
– Stunted growth
– Hyperactivity
– Vomiting and bad breath
Phenylketonuria (PKU)
• Other Important Info.:
• Treatment:
– Babies receive a
special non-milk
formula
– Affected individuals
should eat a special
diet, limited in proteinrich foods and avoid
artificial sweetners.
Phenylketonuria (PKU)
Practice Problem:
A woman has PKU. A
man is completely
normal. What is the
chance of their child
having PKU?
Answer: _____% chance
Albinism
• Recessive disorder
• Symptoms:
– Causes no or little pigment (melanin) in eyes,
skin, and hair
• Blue eyes
• Pale skin
• Light hair
Albinism
• Other Important Info.:
– Sensitive to sun
exposure
– Vision is impaired
Albinism
Practice Problem:
Is it possible for 2
albino people to have
a child with normal
pigment?
Answer: ______% chance