Topic 2C - Genetic Screening

Front 1

What is genetic screening?

Back 1

Genetic screening involves analysing the DNA to see if it contains alleles for genetic disorders.

Front 2

What is carrier testing (identification of carriers)?

Back 2

1. Carrier testing is offered to individuals with a family history of genetic disorders. It shows whether people without a disorder carry an allele that can cause a disorder.
   
2. Couples can be tested before having children to determine chances of future children having the disorder.
   
3. This allows informed decisions to be made about whether to have children and whether to carry out prenatal testing if a woman is pregnant.
   

Front 3

What are the social and ethical issues with carrier testing?

Back 3

• Finding out you're a carrier may cause emotional stress or affect the ability to find future partners.
  
• Tests aren't always 100% accurate which may lead to decisions based on incorrect information.
  
• Other genetic abnormalities may be found, causing further stress.
  

Front 4

What is the preimplantation genetic diagnosis?

Back 4

1. PGD is carried out on embryos produced in IVF. It involves screening embryos for genetic disorders before they're implanted into the woman.
   
2. This reduces the chance of having a baby with a genetic disorder as only embryos without genetic disorders are implanted.
3. Because it's performed before implantations, it avoids the issue of abortion which may be raised by prenatal testing.
   

Front 5

What are the social/ethical issues raised by PGD?

Back 5

1. It can be used to find out other characteristics (gender, eye colour) - leading to concerns that in the future, embryos may be selected for characteristics (designer babies).
   
2. False results could provide incorrect information.
   

Front 6

What is prenatal testing?

Back 6

Prenatal tests involve screening unborn babies for genetic disorders.

They're offered to pregnant women with a family history of genetic disease.

There are two types of tests - amniocentesis and chorionic villus sampling.

Front 7

What is amniocentesis?

Back 7

1. Usually carried out at 15-20 weeks of pregnancy.
   
2. A sample of amniotic fluid is obtained via the abdomen using a needle.
   
3. The fluid contains fetal cell containing DNA, which can be analysed.
   
4. Has a 1% risk of miscarriage.
   
5. Results aren't available till after 2-3 weeks, although a rapid test can be made.
   

Front 8

What is chorionic villus sampling (CVS)?

Back 8

1. CVS is usually performed at 11-14 weeks of pregnancy.
   
2. Because it is taken earlier, an earlier decision to abort can be made, so the procedure is less traumatic.
   
3. A sample of cells is taken from the chorionic villi, containing fetal DNA, which is then analysed.
   
4. This is either done via the abdomen or the vagina. CVS has a 1-2% risk of miscarriage. Initial results are available after a few days, but in-depth results take two weeks or more.
   

Front 9

What are the social/ethical issues with prenatal testing?

Back 9

Prenatal testing slightly increases the risk of miscarriage.

False results could provide incorrect information.

Some people consider it unethical to abort a fetus because it has a genetic disorder.