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

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?

Answer: ______ % chance

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

• 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?Answer: _____% chance

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 Tay-Sachs 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 protein-rich 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