Transcript Slide 1

Human Heredity and Genetic Disorders
•Pedigree Charts
show patterns of
inheritance
•Pedigree Charts
show that presence
or absence of certain
traits
•Pedigree Charts
make it possible to
show the carriers of
recessive genes.
•Males are usually
square and females
are usually a circle
Mrs. Degl
Examples of Human Genetic Disorders
1. Sickle-cell Anemia
•This is a blood disorder found
mostly in African Americans.
•It is caused by a gene
mutation that results in the
production of abnormal
shaped red blood cells.
•These sickle cells cannot
carry O2 efficiently, resulting in
anemia, and severe pain.
Mrs. Degl
2. Tay-Sachs Disease
•A recessive genetic disease
in which nerve tissue in the
brain deteriorates because of
an accumulation of fatty
material.
•The disorder is a result of
the body’s inability to
synthesize a particular
enzyme.
•It is fatal
•It occurs mostly among
Jewish descent.
Mrs. Degl
3. PKU (Phenylketonuria)
•A disorder in which the body cannot synthesize the
enzyme necessary to metabolize (break down) the amino
acid phenylalanine.
•Without this enzyme, phenylalanine accumulates in the
blood and body tissues.
•This disease is homozygous recessive and causes severe
mental retardation if not detected at birth.
•If detected at birth, retardation can be prevented by
maintaining a phenylalanine free diet.
•Classic PKU affect about one of every 10,000 to 20,000
Caucasian or Oriental births. The incidence in African
Americans is far less.
Mrs. Degl
Detecting Genetic Disorders
1. Screening: Blood or urine screening can detect certain
genetic disorders like PKU, Sickle-cell Anemia, and TaySachs Disease.
2. Karyotyping: A greatly enlarged photograph of
chromosomes is viewed and examined to see if there are
any abnormalities in number or structure.
3. Amniocentesis: A technique in which a small sample of
amniotic fluid is taken from the amniotic sac of a pregnant
woman. The fluid contains fetal cells which can be
examined with karyotyping. Sickle-cells, Tay-Sachs
Disease and Down Syndrome can be detected this way,
among other abnormalities.
4. Genetic Screening: The techniques above, along with
pedigree charts are used by genetic counselors, for
couples with genetic disorders in their families.
Mrs. Degl