Screening Patients (AQA A Level Biology): Revision Note

Genetic screening

• Certain circumstances (e.g. in the pregnancy of an older woman, or pregnancy where there is a family history of a genetic disease) may require individuals to determine if they have a particular allele present in their genome. This can be determined by genetic screening

• Genetic screening is the testing of an embryo, fetus or adult to analyse the DNA

• Genetic screening can help identify individuals who are carrying an allele at a gene locus for a particular disorder

• The sample of DNA to be analysed can be obtained by:

  • taking tissue samples from adults or embryos produced by in vitro fertilisation

  • chorionic villus sampling or amniocentesis of embryos and fetuses in the uterus

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

Example: Breast cancer (BRCA1 and BRCA2)

• BRCA1 and BRCA2 are genes that produce tumour suppressor proteins, and thus they play an important role in regulating cell growth

• Faulty alleles of these particular genes exist, which increase the risk of an individual developing breast and ovarian cancers during their lifetime

• Faulty BRCA1 and BRCA2 alleles can be inherited from either parent

• The advantages of genetic screening for an adult who has a family history of BRCA1 and BRCA2 gene mutations:

  • The person may decide to take preventative measures (e.g. by having an elective mastectomy – breast removal – to reduce the risk of developing cancer)

  • Screening for breast cancer may begin from an earlier age or more frequently, and the individual (if female) will have more frequent clinical examinations of the ovaries

  • It enables the person to participate in research and clinical trials

Evaluating the use of genetic screening

• Although genetic screening has a wide range of benefits, there are also potential disadvantages of this technology, and its use has been questioned by many people who believe it to be potentially dangerous or unethical

Advantanges

• Screening for certain conditions can enable people to make sensible lifestyle choices to reduce the chances of the disease developing

  • For example, if you are found to be genetically predisposed to getting cancer or developing heart disease, you can decide to eat a healthy diet and refrain from smoking to reduce the chances of these diseases developing

• Screening enables potential parents to choose whether or not to have biological children, as they may not want to risk passing on a harmful allele

• Screening enables people to participate in research and clinical trials, which are critical for developing an understanding of and treatments for genetic disorders

Disadvantages

• There may be nothing positive that can be done in response to information discovered during genetic screening, potentially leading to the person becoming depressed or scared

• The results of a genetic screen may lead to a higher price for life insurance (which they may not be able to afford) than other people

• Some people fear that screening may lead to a form of genetic discrimination against individuals with defective or disease-causing alleles (which may be seen by some people as being "inferior", although this is not the case and no-one should ever be seen as being genetically inferior)

  • In addition, parents found to have a high chance of passing on harmful alleles may be unfairly pressured into not having children

• Screening may be used to look more broadly at the genetic make-up of a potential child (i.e. not just focusing on the risks of genetic disorders developing), which could eventually lead to potential parents making reproductive decisions such as aborting foetuses that do not have the desired genetics

  • This idea of 'designer babies' becoming a possibility in the future raises many ethical questions

• Some religions consider such interferences with the natural process of reproduction to be highly immoral