Transcript Human Genetic Disorders

Human Genetic
Disorders
Biology
Mutations
• Sometimes genes are damaged or copied
incorrectly.
• A change in a gene is called a mutation.
• Mutations are a source of the variation a
species needs in order to adapt to changing
conditions over time.
• Most mutations are harmful or neutral, only
rarely are they beneficial.
Recessive Mutations
• Most mutations are passed from parent to
offspring without being expressed.
• Although rare, most people are probably
carriers for a number of genetic mutations.
• It is unlikely that two individuals with the same
unexpressed mutation will mate and produce
an offspring expressing the mutation.
Genetic Disorders
• Particular mutations have become more
common in human populations.
• The harmful effects that some mutations
produce are called genetic disorders.
• A person with a genetic disorder has inherited
a defective gene from both parents.
Cystic Fibrosis
• Caused by a faulty transport protein.
• This mutation causes mucus
accumulation in the lungs and pancreas,
causing difficulty breathing and blocking
proper food digestion.
• There is no cure, only treatment of
symptoms.
Sickle Cell Anemia
• Results from faulty hemoglobin.
• This mutation causes the body to make an
abnormal form of hemoglobin, making red
blood cells looked deformed.
• Sickled cells are fragile and break down easily.
• Symptoms include fatigue, headaches, muscle
cramps, and sometimes kidney or heart
failure.
Hemophilia
• Results from a fault blood-clotting protein.
• This mutation causes the body to build a defective
form of a protein needed to clot blood.
• Small cuts do not heal well and internal bleeding can
be fatal.
• This trait is sex-linked, meaning it is transmitted on the
X chromosome. Only boys will develop the disorder.
• There is treatment and children with hemophilia can
lead normal lives.
Down Syndrome
• A genetic disorder caused by an extra
chromosome 21.
• Features include extra folds in the upper
eyelids, broad flattened noses, short stature,
and varying degrees of mental retardation.
• Occurs in about 1 of every 1,000 births and is
more common among babies born to older
mothers. Mothers 45 and older have a 1 in 16
risk of having a child with Down Syndrome.
Genetic Counseling
• A genetic counselor can prepare a family
pedigree or record that shows inheritance
patterns over several generations. This can
help determine the chance of being a carrier
for that disorder.
• We also have genetic testing now and we can
test for the presence of specific genes known
to cause genetic disorders.
Finding Cures
• Most genetic disorders cannot be cured.
• Therapy is available for some.
• Techniques in genetic engineering can make it
possible to cure genetic disorders by replacing
copies of defective genes with copies of
healthy ones.
• Gene therapy is an evolving science.