Module 3 Genetic Screening
----one way to allow couples to have offspring free of certain diseases

Related topics: basic genetics, applied genetics, reproduction in human, techniques in modern biotechnology, bioethics

Guiding questions:
What is genetic screening?
Who should carry out genetic screening?
What are the ethical concerns of having genetic screening?

Introduction

What is genetic screening?

Genetic screening 遺傳篩檢 allows one to choose a person fitting certain criteria in genotype.  This can be done for couples having in vitro fertilization, called Preimplantation Genetic Diagnosis (PGD) 胚胎著床前遺傳診斷.  A cell from an eight celled embryo is first extracted and its DNA will be analyzed for the presence of one or more disease associated gene 疾病相關基因. Only those embryos with no disease genes concerned will be implanted into mother’s uterus.

Recently, the whole genome of an embryo can also be predicted by analysing DNA from mother’s blood and DNA from father’s saliva.  In this way, the embryos under natural conception 自然受孕 can also be checked whether they are carriers of certain disease genes.  If serious defects 缺陷 are found in those embryos, parents may consider early treatments or abortion.

One way of analyzing DNA of an individual is called DNA fingerprinting 指紋分析. The process of DNA fingerprinting will be introduced in the   Virtual lab  .

Couple fitting the following criteria would be suggested to have PGD:

  1. They are carriers of certain disease genes.
  2. The embryos in previous pregnancies had chromosomal abnormality 染色體異常.
  3. The mother has recurrent miscarriages 流產.
  4. The mother experiences repeated implantation failure 反覆着床失败.

Controversy on genetic screening

Ethical concerns exist towards genetic screening. Some people say it interferes with the course of Nature and some concern about the issue of having “designer babies”.

Questions arise on what should be screened:

  1. Which diseases should be screened? Is reading difficulties and emotional problems a kind of disease?
  2. Could the traits 特質 like sex, eye colour or intelligence be screened?

After the screening process, embryos carrying the disease gene or undesired traits will be disposed or frozen. Is that a moral way to treat potential human life?

>>Case study