Term
| Types of Screening and Testing |
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Definition
Gamete Testing
Preimplantation Genetic Diagnosis
Prenatal Testing
Newborn Screening
Carrier Testing |
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Term
| Preimplantation Genetic Diagnosis (PGD) |
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Definition
Done prior to implantation in a laboratory setting at the 8-cell
blastomere stage after fertilization
A single cell is suctioned off during the 8-cell stage and tested
for specific genetic diseases.
All cells of the blastomere are identical under normal
circumstances; if the tested cell is missing the “bad” gene, then
the entire embryo is missing that gene and it is a candidate for
implantation.
What to do with unused embryos is an ethical concern. |
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Term
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Definition
This procedure is done during the pregnancy after about the
12th week (there must be enough fluid in the amniotic sac and
extra space).
A fiber optic camera is placed into the uterine cavity to
produce a video in real time.
During this procedure doctors can do surgery on the fetus
while it is still in the uterus. Doctors can also medicate directly
to the child through placental blood vessels.
The camera cannot injure the child. An abdominal incision on
the mother is required for insertion. Infection is possible. |
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Term
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Definition
Throughout the pregnancy. This procedure is often done at
regular check ups prior to birth.
Sound waves are transmitted through the mother’s abdomen
and bounce back when they hit an obstruction. This bouncing
back creates a picture.
Many things can be measured from the picture created.
This procedure is safe and noninvasive. |
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Term
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Definition
This procedure is done in a lab on the gamete prior to
fertilization or implantation.
Eggs are removed from the female body. The polar body is
removed from its place inside the zona with the egg. The polar
body is then tested for specific genes.
If the polar body has the “bad” allele and the female is
heterozygous in the trait, the “good” allele must be in the egg.
Helps in determination of which eggs to use in fertilization and
implantation.
Complex and costly procedure. The woman must take high
dose hormones, go under general anesthesia, have surgery,
and then later be implanted with the fertilized product. |
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Term
| Chorionic Villi Sampling (CVS) |
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Definition
With use of an ultrasound, a doctor samples the placenta
either abdominally or vaginally.
The placenta will have the same DNA as the child. The sample
can give information about the child’s DNA.
This procedure is still very safe, however if the placenta is
disrupted, the child can spontaneously abort. Infection is also
possible. |
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Term
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Definition
Can be done at any time throughout the pregnancy.
Blood is taken from the mother’s vein.
Sometimes fetal cells are present in mom’s blood and these
fetal cells can be used in chromosomal analysis.
Very inexpensive and noninvasive procedure with quick results
and no risk of harm to the fetus. |
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Term
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Definition
In the United States this is mandated by law and done within a few
days following the child’s birth. Can also be done voluntarily.
The newborn’s heel is pricked and the blood is collected on a card.
The blood is then used in genetic testing for specific diseases like
PKU and hypothyroidism.
The tests mandated by law only look for genetic problems that
can be fixed by medication or diet. If a disease is caught, it can be
treated and potentially save the child’s life.
Discomfort to the fetus when pricked is common, however there are
no major safety concerns. The use of the cards after screening is an
ethical concern. |
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Term
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Definition
Cannot be done until the 16th week so there will be enough
fluid for a sample.
With use of an ultrasound, a needle is inserted through mom’s
abdomen into the amniotic sac and amniotic fluid is extracted.
There will be fetal cells in the fluid that can be tested using
chromosomal analysis. The fluid can be tested biochemically.
These results can show diseases and abnormalities of the
developing fetus.
The procedure leaves a hole in the amniotic sac that has to
heal. Infection is possible as well as pricking the child with the
needle. |
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Term
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Definition
fertilization or implantation.
A man give a sperm donation that can then be sorted and
tested.
Can get rid of sperm with morphologic defects. Can sort sperm
into X and Y if a certain sex child is desired. Sperm can be
tested for a “bad” gene.
This is a noninvasive procedure that is very inexpensive. There
is little ethical concern with getting rid of extra sperm because
a sperm itself cannot become a child. |
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