inheritance genetic-screening

Genetic Screening: Uses

• Some circumstances, e.g. in a pregnancy where there is a family history of a genetic disorder, may require individuals to determine if they have a particular allele present in their genome

• This can be determined by genetic screening

• There are three main uses of genetic screening

  • Identifying individuals who are carrying an allele at a gene locus for a particular disorder

  • The screening of embryos prior to implantation during fertility treatment; this is Preimplantation Genetic Diagnosis (PGD)

  • Testing a foetus before birth; this is prenatal testing

Identification of carriers

• Carrier testing is offered to individuals with a history of genetic disorders in their family

• It can show whether people who have no symptoms carry the allele for particular disorders, such as cystic fibrosis

• Couples can be tested prior to having children to determine the probability of future children inheriting the disorder

• Benefits

  • Families can make informed decisions before having children

  • Women can decide whether to have prenatal testing during pregnancy

Preimplantation Genetic Diagnosis

• IVF, or in vitro fertilisation is a type of fertility treatment during which fertilisation is carried out in the lab; embryos produced in this way can be implanted into the uterus where they develop into a foetus

• PGD involves analysis of the DNA of an embryo prior to implanting it into the uterus

  • The sample of DNA to be analysed can be obtained by taking cell samples from embryos produced during IVF

• Benefits

  • Reduces the chances of having a baby with a genetic disorder

  • It avoids abortion as it is carried out before implantation of the embryo

Prenatal testing

• Prenatal testing is offered to pregnant women with a family history of genetic disorders

• It involves testing the foetus for genetic diseases

• The DNA can be obtained by chorionic villus sampling or amniocentesis of embryos and foetuses in the uterus

• Chorionic villus sampling

  • This involves removing and testing a small sample of cells from the placenta using a fine needle

  • The cells contain foetal DNA which can be analysed for genetic disorders, allowing parents to make informed decisions about the pregnancy and foetus

  • It is carried out at around 11-14 weeks of pregnancy

  • The process has a 1-2 % risk of miscarriage

• Amniocentesis

  • This involves removing and testing a small sample of cells from amniotic fluid using a fine needle

    • The amniotic fluid is the fluid that surrounds the foetus within the uterus

  • The fluid contains foetal cells which contain DNA to be analysed

  • It is carried out at around 15-20 weeks of pregnancy

  • The procedure has a 1% risk of miscarriage

• Benefits

  • The tests allow parents to make informed decisions

  • Results can help parents prepare for the future care of the child, including medical treatment

Genetic Screening: Social & Ethical Issues

• Genetic screening comes with a range of different social and ethical issues

• As genetic screening can leave future parents with many questions, genetic counsellors are available to help

  • Counsellors can be seen before screening has occurred; they may discuss the following with the prospective parents

    • The probability of the couple having a child with a genetic disorder

    • Termination of the pregnancy

    • Therapeutic treatments possible for the child

    • Financial implications of having the child

    • Effect on existing siblings

    • Ethical issues

  • After screening the counsellors will read the results and explain them to the future parents

• Each use of genetic screening brings potential concerns that should be considered

  • Identification of Carriers

    • Finding out you are a carrier can cause emotional stress and upset

    • It may impact your ability to find a partner 

    • Other genetic disorders may be identified 

    • Employers and insurance companies may use the data against an individual 

    • The tests are not always 100 % accurate; false positives or negatives may be given

  • Preimplantation Genetic Diagnosis

    • There are concerns it could lead to “designer babies” where parents select embryos with certain traits such as eye colour or sex

    • False results could lead to inaccurate information and poor decisions being made about the fate of embryos

  • Prenatal testing

    • Each procedure brings risk of miscarriage

    • False results could provide inaccurate information and poor decisions being made

    • There are ethical implications involved if parents decide to abort the fetus