IN Today we will be studying several common genetic disorders inherited by humans. –How do you think a FAMILY is impacted when a child in the family is.

IN• Today we will be studying several

common genetic disorders inherited by humans.– How do you think a FAMILY is impacted

when a child in the family is diagnosed with a genetic disorder?

– What types of changes in the household will they need to make?

– What types of changes in their daily lives could occur?

OUT• Cystic Fibrosis is a recessive genetic

disorder. During routine blood work tests, a pregnant woman found out she is a carrier for cystic fibrosis. Her husband then had his blood tested and he is ALSO a carrier for cystic fibrosis. (Neither parent knew this information before.) – If you were her obstetrician (baby doctor) how

would you explain the results to this woman. – What probabilities would you tell this worried

couple? – Use a Punnett Square to support your answer.

HUMAN GENETIC DISORDERS

CLASS NOTES – PAGES 151-155

What is a Genetic Disorder?

• Abnormal condition that a person inherits through genes or chromosomes

What causes a genetic disorder?

1. Mutations:– Changes in a

person’s DNA

2. Or the overall structure or number of chromosomes

Who can get genetic disorders?• Anyone

– Parents could be carriers for a disorder and pass it on to their children

OR– The disorder could happen by chance

with no reason whatsoever.

• Symptoms of the disorder could be seen prenatally (pre-birth), at birth, not be seen into childhood or in rare cases, not be seen until adulthood.

We will examine several genetic disorders.

• We will look for the following information:– How is the disorder

inherited?– What are the characteristics

of someone who has inherited this disorder?

– What are the treatments for someone who has inherited this disorder?

Examples of Human Genetic Disorders

•Cystic Fibrosis– Caused by a recessive

allele on one chromosome

– Affects the body’s ability to move salt and water in and out of the cells

– Thick mucus forms in the lungs and intestines

– Makes it difficult for that person to breathe

Cystic Fibrosis (CF)• About 3,000 babies

are born each year with cystic fibrosis

• More than 10,000,000 healthy people are unknowingly carriers of this disorder

• Each time 2 carriers conceive there is a 25% chance that their child will have CF

Cures for CF?• There are NO cures for

CF, but there are treatments

• Patients can have breathing treatments administered

• Chest therapy must be done each day to clear the mucus from their lungs

A day in the life..

Sickle Cell Anemia– Affects the blood– People with the disease

form an abnormal type of hemoglobin (the part of the blood that carriers oxygen)

– They suffer from lack of oxygen and experience pain and weakness (called a sickle-cell crisis)

Sickle Cell Anemia• Sickle-cell Disease

– A co-dominant trait. Person must inherit BOTH alleles for the disease to have it.

– A person with one of the alleles will produce BOTH types of cells but will not show signs of the disease.

Sickle-Cell Disease• More than 70,000

Americans have sickle-cell disease

• Affects people mostly of African ancestry

• 1 in 12 African Americans are CARRIERS for the disorder

What is Anemia?• Unlike normal blood

cells that last for about 4 months, sickle cells break down after 10-20 days.

• This causes anemia: – When the RBC’s

count falls below normal.

– Person feels weak and tires more easily

Cures for Sickle-Cell Disease?

• There are No cures for sickle-cell disease, but there are several forms of treatment– Blood transfusions– Antibiotics

• Penicillin starting from 2 months old

– Proper nutrition, bedrest, protection against infection, avoidance of extreme cold and extreme hot temperatures

A day in the life…

Duchenne Muscular Dystrophy• Involves muscle weakness

that gets worse over time.• A defective gene causes the

person to not make a protein called dystrophin

• Recessive Sex-linked trait– Males are more likely to

inherit this disorder than females.

• Occurs in approximately 1 out of 3600 male infants

50% 50%

50% 50%

Symptoms of DMD• Fatigue • Muscle weakness

– Begins in the legs and pelvis, but also occurs less severely in the arms, neck, and other areas of the body

– Difficulty with motor skills (running, hopping, jumping) – Frequent falls – Rapidly worsening weakness

• Progressive difficulty walking – Ability to walk may be lost by age 12

• By age 10, the person may need braces for walking. By age 12, most patients are confined to a wheelchair.

A day in the life…

Examples of Genetic Disorders

• Hemophilia– Affects the blood– People with the disorder

do not have blood that properly clots, they are missing a clotting factor

– Left untreated, people with the disease could bleed to death from a cut or gash

– Sex-linked trait: Recessive allele carried on the X chromosome

Hemophilia• There are

approximately 20,000 hemophilia patients in the United States (400,000 world wide)

• About 400 babies are born each year with the disorder

• Symptoms include large bruises, swelling in the joints, and internal bleeding

Cures for Hemophilia?• There are no cures for

the disorder. Treatments include:– replacing the missing

clotting factor in the blood. This is done by injecting a product that contains the needed factor into a vein. Bleeding stops when enough clotting factor reaches the affected area.

A Day in the Life…

Examples of Human Genetic Disorders• Down’s Syndrome (Trisomy

21)– Extra copy of

Chromosome 21– Symptoms include:

• Facial defects• Mental retardation• Hearing/sight

problems• Heart defects• Various infections

– Occurs in 1 out of every 1000 births

– Life expectancy is about 55 years old

A day in the life…

Pedigrees: a chart or family tree that tracks which members of a family have a particular trait.

Diagnosing Genetic Disorders

• Amniocentesis:– Doctors use a long

needle to remove some fluid from around the baby

– They test the fluid for genetic disorders because the fluid contains cells from the baby

– From that test, a karyotype is created.

What is a karyotype• A picture of all

the chromosomes in a cell.

• Reveals whether the person has the correct number of chromosomes in their cells. Is this a karyotype of a

male or female? How do you know?

Genetic CounselingPregnant women will have many pre-natal tests done while pregnant.

• These tests will look at the blood work, urine analysis, diet and overall health of the mother to determine protein levels, blood production, chromosomal number, etc. in the fetus.

If the medical tests on the mother suggest more genetic testing, than the couple may be referred to a genetic counselor.

•Someone who works with the medical team to help families who are risk for having offspring with genetic disorders.

Role of the genetic counselor…

• evaluating family history and medical records

• ordering genetic tests • evaluating the results

of this investigation • helping parents

understand and reach decisions about what to do next