Genetic Disorders
What is a Genetic Disorder?
• Caused by abnormalities in an individual’s
genetic material (the DNA, or the genome).
• There are four different types of genetic
disorders:
▫ Single-gene is mutated
▫ Multifactorial problems
▫ Chromosomal changes-entire areas of the
chromosome can be missing or misplaced.
▫ Teratogenic problems
Single Gene Mutation
• A single gene is responsible for abnormality
• Greater risks of inheritance
• Dominant: One of the genes from the parent is
abnormal
• Recessive: Both parents have abnormal genes.
• X-linked: Determined by the genes on the X
chromosome. (Mainly affects males)
Multifactorial Problems
•
•
•
•
Multiple genes mutated
Environmental effects
Other unknown factors
Examples:
▫ Heart defects
▫ Cleft lip or cleft palate
▫ Neural tube defects
Chromosomal Abnormalities
•
•
•
•
May be inherited or occur with no family history
Aneuploidy: More or few chromosomes than normal
Deletion: Part of a chromosome is missing
Inversion: Chromosome breaks and reattaches itself
upside down
• Translocation: Rearrangement of a chromosome
segment from one location to the other
• Mosaicism: Presence of two or more chromosome
patterns in the cells of a person
Teratogenic Problems
• Occur when the baby is exposed to certain
substances
• During the first trimester- organs are forming
• Known teratogens:
▫
▫
▫
▫
▫
Certain medications
Alcohol
Radiation
Lead
Certain infections
Top Ten Most Common Genetic
Disorders
1.
2.
3.
4.
Cystic Fibrosis
Huntington’s Disease
Down Syndrome
Duchenne Muscular
Dystrophy
5. Sickle Cell Anemia
6. Celiac Disease
7. Becker Muscular
Dystrophy
8. Noonan Syndrome
9. Thalassemias
10. Turner Syndrome
Cystic Fibrosis
• Affects the cells that produce
mucus, sweat, and digestive
juices.
• Secretions are thick and
block tubes, ducts, and
passageways.
• Symptoms:
▫
▫
▫
▫
Difficulty breathing
Recurrent lung infections
Digestive issues
Reproductive issues
Huntington's Disease
• Causes the progressive breakdown of nerve cells
in the brain
• Can cause:
▫ Problems with movement
▫ Thinking disorders
▫ Psychiatric disorders
• Usually develop signs and symptoms around age
30 or 40
Down Syndrome
• Abnormal cell division results
in extra genetic material from
chromosome 21
• Leads to:
▫ Lifelong intellectual
disabilities
▫ Developmental delays
▫ Some health problems
• There are some common
features that are a result of
Down syndrome
Duchenne Muscular Dystrophy
• Causes progressive weakness and loss of muscle
mass
• Symptoms usually begin in childhood (age 2-3)
• Typically affects boys
• Symptoms:
▫
▫
▫
▫
▫
Frequent falls
Trouble running and jumping
Muscle pain
Large calf muscles
Walking on the toes
Sickle Cell Anemia
•
•
•
•
Lack of healthy red blood cells to carry oxygen
Blood cells become rigid and sticky
No cure but treatments can relieve pain
Symptoms:
▫
▫
▫
▫
Episodes of pain
Frequent infections
Vision problems
Delayed growth
Celiac Disease
• Immune reaction to eating gluten
• Inflammation of the small intestine when gluten
is consumed
• Can deprive other important organs of nutrients
• Symptoms:
▫
▫
▫
▫
▫
Digestive problems
Headaches and fatigue
Diarrhea
Weight loss
Swollen belly
Becker Muscular Dystrophy
• Degenerative disease that affects voluntary
muscles
• Onset is late childhood or adolescence
• Gets worse at a much slower rate than DMD
• Symptoms:
▫
▫
▫
▫
Difficulty walking (usually unable at age 30)
Loss of muscle mass
Frequent falls
Muscle weakness
Noonan Syndrome
• Prevents normal development
• May cause:
▫
▫
▫
▫
Unusual facial characteristics
Short stature
Heart defects
Other physical problems
• About 80% people affected
have congenital heart disease
Thalassemia
• Blood disorder
▫ Less hemoglobin
▫ Fewer red blood cells
• Can cause anemia
• Symptoms:
▫
▫
▫
▫
Fatigue
Weakness
Pale appearance
Facial bone deformities
Turner Syndrome
• Only affects females
• Occurs when the X chromosome is missing or
partially missing
• Can be found before birth
• Symptoms:
▫
▫
▫
▫
▫
Delayed growth
Heart defects
Learning disabilities
Short stature
Web like neck
References
• http://www.activebeat.com/yourhealth/children/the-10-most-common-geneticsdisorders/
• http://www.doctorslounge.com/studlounge/do
wndirty/genetic.htm
• http://www.urmc.rochester.edu/encyclopedia/c
ontent.aspx?ContentTypeID=90&ContentID=P0
2505