2.15, 2.16 Genetic Screening Flashcards
2.15 i) Understand the uses of genetic screening, including the identification of carriers, pre-implantation genetic diagnosis (PGD) and prenatal testing, including amniocentesis and chorionic villus sampling. ii) Understand the implications of prenatal genetic screening. 2.16 Be able to identify and discuss the social and ethical issues related to genetic screening from a range of ethical viewpoints.
What is genetic screening?
testing for the presence of an abnormal mutated allele that causes a genetic disease
When is genetic screening often offered?
to individuals with a family history of genetic disorders
What are the uses of genetic screening?
- the identification of carriers
- preimplantation genetic diagnosis
- prenatal testing
- to confirm a diagnosis
How is genetic screening used to identify carriers?
- DNA in blood/cheek cells are used to detect abnormal alleles in carriers
- shows whether people without a disorder carry an allele that can cause a disorder
What are the advantages of carrier testing?
- couples can be tested before having children to determine the chances of any future children having the disorder
- this allows people to make informed decisions about whether to have children or whether to carry out prenatal testing
What are the social and ethical issues of carrier testing?
- finding out you are a carrier can cause emotional distress
- tests are not always 100% accurate, so could give false positives, which means decisions would be based on incorrect information
- results of genetic tests could be used by employers or life insurance companies resulting in genetic discrimination
- other genetic abnormalities could be found, causing emotional distress
What is preimplantation genetic diagnosis?
- PGD is carried out on embryos produced by in vitro fertilisation - iVF
- it involves screening the DNA in embryos for genetic disorders before they are implanted into the mother
What are the advantages of PGD?
- reduces the chance of a baby having a genetic disorder, as only embryos without the genetic disorders will be implanted
- because it performed before implantation, it avoids the issue of abortion that could be raised by prenatal testing
What are the social and ethical issues of PGD?
- it could be used to find out other characteristics such as eye colour, leading to concerns over designer babies in the future
- religious or ethical concerns over discarding embryos not used for implantation
- false results could provide incorrect information, and the embryos implanted may still have the disorder
What is prenatal testing and what are the two types?
- screening unborn babies for genetic disorders
- amniocentesis
- chorionic villus sampling
What is amniocentesis? When is it carried out? What are the risks of miscarriage? When are the results available?
- a sample of amniotic fluid (the fluid that surrounds the fetus) is obtained via the abdomen using a fine needle
- the fluid contains fetal cells, whose DNA can be analysed and screened for disorders
- carried out at 15-20 weeks
- 1% risk of miscarriage
- results available after 2-3 weeks from test
- rapid tests (only looks at common disorders) take 3-4 days after test
What is chorionic villus sampling? When is it carried out? What are the risks of miscarriage? When are the results available?
- a sample of cells is taken from the chorionic villi (the part of the fetus connecting it to its mother)
- the cells contain fetal DNA which can be analysed and screened for disorders
- the procedure is done either from the abdomen using a fine needle, or the vagina using a catheter
- carried out at 11-14 weeks (so an earlier decision can be made to abort compared to amniocentesis)
- 1-2% risk of miscarriage (> amniocentesis)
- initial results regarding major issues in a few days, detailed tests take up to 2 weeks or more
What are the social and ethical issues of prenatal testing?
- increase risk of miscarriage
- false results could provide incorrect information
- religious or ethical issues regarding abortion of a fetus due to the discovery of a genetic disorder
How does prenatal testing help people make decisions?
- allow them to make informed decisions
- can make decisions regarding abortion
- can make decisions regarding future care and help parents prepare for any medical treatment available after the child is born
