Transcript 6.2 Human Genetic Disorders

7.2.d Students know plant and animal cells
contain many thousands of different genes and
typically have two copies of every gene. The
two copies (or alleles) of the gene may or may
not be identical, and one may be dominant in
determining the phenotype while the other is
recessive.
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Genetic disorder- an
abnormal condition that a
person inherits through
genes or chromosomes
Key concept: “Some genetic
disorders are caused by
changes in the DNA of
genes. Other disorders are
caused by changes in the
overall structure or number
of chromosomes.”
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CYSTIC FIBROSIS
caused by a recessive
allele as a result of a
mutation
body produces
abnormally thick mucus
in the lungs and
intestines
makes it hard to breathe
SICKLE-CELL DISEASE
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codominant with
normal cells
person with two
sickle-cell alleles has
the disease
person with one
sickle-cell allele has
both normal and
abnormal hemoglobin
unusual shaped blood
cells that clogs the
blood vessels
HEMOPHILIA
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Caused by a recessive
allele on the X
chromosome
Sex-linked
Blood cots very slowly
or not at all
Person doesn’t produce
one of the proteins
needed for clotting
DOWN SYNDROME
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Extra copy of
chromosome 21
Most often happens
when a chromosome
fails to separate during
meiosis
• Pedigree- a chart that tracks members of a family with
a particular trait
• Key Concept: “One important tool that geneticists use
to trace the inheritance of traits in humans is a
pedigree.”
• Pedigrees can be
about normal traits
like widow’s peak
or genetic disorders
•
This pedigree shows the
inheritance of hemophilia in
a family.
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Key Concept: “Today, doctors use tools such as
karyotypes to help diagnose genetic disorders.
People with genetic disorders are helped
through medical care, education, job training,
and other methods.”
Doctor’s use Punnett squares and pedigrees to
help predict whether a child might have a
genetic disorder or not
Karyotype- a picture of all the chromosomes in
a cell showing if a person has the correct
number of chromosomes or not
Genetic counseling
 Families that have a
history of a genetic
disorder
 Help people understand
the chances of having a
child with a specific
disorder
 Use Punnett squares,
pedigrees, karyotypes to
help
Karyotyping
Punnett square
Pedigree
Dealing with Genetic Disorders
• Deal with serious
challenges
• Modify
environment
• Medicine, diet, and
vitamins
• Education
• People can still live
active and
productive lives
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A pedigree is a chart or “family tree” that tracks
which members of a family have a particular
trait.
What are two major causes of genetic
disorders in humans?
How do geneticists trace the inheritance
of traits?
How are genetic disorder diagnosed
and treated?