Transcript Scenario continued

Scenario
Paul is rushed into intensive care where a diagnosis of acute myocardial infarction (heart
attack) is made. His cholesterol level is 325mg%, and for a man of his age and lifestyle,
it should be well under 200mg%. Stacy calls the genetics center because Paul’s
cardiologist placed much emphasis on a review of Paul’s family history. He told Stacy
that “Paul’s case looks like the type that runs in families. It amounts to an inherited
tendency to early heart disease. By the way, how many children did you say you
have…?”
Scenario continued
Paul’s mother was revealed to have had a coronary bypass at the age
of 57. She is adopted and no further information about her family is
known.
This type of familial
hypercholesterolemia (FH) is
determined by a single, autosomal
dominant gene and that each of Paul’s
children has a 50% chance of having
inherited the gene.
Familial Hypercholesterolemia (FH)
• Cholesterol
levels
unregulated
– Builds up
• Gene on
chromosome
#19
• Potentially fatal
• Autosomal
dominant
Paul: Heterozygous for familial hypercholesterolemia
Stacy: Healthy
FH
FH
Key
F = FH disease
f = normal
normal
normal
Scenario
Paul’s condition stabilizes and long term dietary and drug
treatment is planned.
Plans are made to test other “at-risk” family members, in order to
identify those who have inherited the gene and who could benefit
from aggressive management.
Look at it this way…your
I exercise. I eat right. I
healthy lifestyle may have
thought my healthy
actually postponed the heart
lifestyle would have
attack or reduced its severity.
protected me from this.
This is very depressing.
Scenario
Paul had a younger brother, John, who died several years ago at the
age of 18 in a car accident. He had fragile X syndrome, and was
moderately retarded.
Scenario
Paul had a younger brother, John, who died several years ago at the age of 18 in a car
accident. He had fragile X syndrome, and was moderately retarded.
Fragile X
• Defected gene
on X
chromosome
• Recessive
sex-linked
• Protein absent
• Mental
retardation
Fragile X
Scenario continued
Paul has a sister, Susan, who is 18 and another sister, Deborah, 19. Both are
offered lipid testing to determine if either has inherited the gene for FH.
Susan is found to have normal levels of lipids (fatty acid substances, including
cholesterol) in the blood. Years ago, when John was diagnosed with Fragile X
syndrome, she had her chromosomes tested to determine if she might carry a
gene for Fragile X. The chromosome study had been normal.
OK. I’ll
have my
lipids
tested.
Scenario continued
Deborah had been offered Fragile X chromosome testing
when her brother was alive to see if she might be a carrier.
She had refused Fragile X testing at that time as well.
If my life is shortened byNo.
heart
I don’t want to be tested.
disease,My
I’m brother
sure I’ll Johnnie,
be Medical
reincarnated
hescience
hadasa is stupid and silly.
a Galapagos turtle or something
else
get now
all my
questions
answered by
rough life but II bet
he’s
a
that lives a long time, because
y’know,and visions.
myormedicines
lion or a dolphin
something
everything balances out.
great like that.
Scenario continued
Plans are made to test Stacy’s children.
Go ahead and test
Michelle and Alan. I
don’t think that you
need to test Frank.
I understand that. It’s just
that…well…there’s a
good chance that Paul
isn’t Frank’s father…”
Are you sure?
Remember the
Punnett Square I
showed you
earlier? Every
one of your
children has a
50% chance of
inheriting the
gene for FH.
Including Frank.
Random practice problem
• Huntington’s disease is a dominant disorder found on
chromosome 4. Betty and Marcus met at a support clinic they
have been attending to help them cope with the knowledge of
their illness with Huntington’s disease. They would like to know
the risk of having a healthy child, now that Betty is pregnant.
Hh
Hh
Marcus
Betty
Key
disease
disease
H = Huntington’s disease
h = healthy
disease
healthy
?