Video Transcript
All of the individuals described
below are planning on having children in the near future. Person A has a grandparent who is
an identical twin. Person B has a family history of
thalassemia, a disorder affecting the hemoglobin of the blood. Person C lives in a small community
and is marrying their first cousin. And person D already has two girls
and would like a boy. Which of the people listed above
would most likely be offered genetic screening?
Genetic screening is the process by
which a person’s DNA is studied to identify any genes that could cause a genetic
disorder. It is commonly offered to those
with a family history of a specific illness or disease. Genetic screening can be carried
out either before a couple tries to conceive or during pregnancy. For high-risk parents or those that
are related, these tests are offered in the prepregnancy stage. One type of genetic screening is
called carrier screening. This is used for people with a
history of a genetic disease but who do not have symptoms. So it is unclear if they carry the
allele for that disease. We can see that this description
applies to one of our options. Person B has a family history of
thalassemia.
Genetic screening may also be
offered to those that live in isolated communities or communities that have a
history of a particular genetic disorder. This is because, typically, these
communities are made up of family groups and individuals are highly related. This means that if this grandparent
was a carrier for a recessive genetic disease like Tay–Sachs, they could pass this
on to their children. Their children, shown here, are now
carriers for the disease. But they could pass the allele on
to their own children. If these two individuals who are
cousins were now to have their own children, they have a much higher risk of passing
on two recessive alleles to their children. This means that their offspring are
much more likely to inherit Tay–Sachs disease. This means that genetic testing is
likely to be offered to another one of our individuals, person C, who lives in a
small community and is marrying their first cousin.
Genetic screening is only offered
to those who are at risk of passing on genetic diseases to their offspring. This helps prevent the spread of
disease and allows parents to prepare themselves mentally, physically, and
financially for having a child with a genetic disorder. It is not offered to people who
would like to choose the sex of their child, so we can exclude person D. And we can also exclude person A,
as genetic screening will not be offered to people who are expecting or who would
like twins.
So the correct answer to which
people would be offered genetic screening is person B and person C.
