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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