Should we screen embryos for genetic diseases?

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Should we screen embryos for genetic diseases?

By Vicki – Louise Flowers 11A

Content:

Introduction

DNA, Genes and Alleles 

Inheritance

  What is a Genetic Diseases?

  • What is a PGD? 
  • Advantages and disadvantages of PGD
  • Multifactorial and polygenic disorders
  • Cystic Fibrosis
  • Huntington’s Disease 

Case Study One: Zain Hashmi

Gene Therapy

  • Retroviruses
  • Adenoviruses
  • Adeno-associated viruses
  • Herpes simplex viruses
  • Problems

Case Study: New embryo test to screen for 6,000 diseases

Ethics

Evaluation 


Introduction:

In this coursework I will be looking to see if it is right or wrong for parents-to-be to have their embryos screened for genetic diseases.  Screening for genetic diseases allows couples to see if their unborn baby would suffer from any disorder that runs in the family. There are over 4,000 genetic diseases around to today and over 5 million people are affected each year. There are many people whose opinion is that by choosing how your baby will be is a form of Eugenics.

Sometimes screening embryos can help people make decisions about their future and how their life may change. Using this method can also help save people lives. But genetic screening is also causing problems such as the thinning of the gene pool and removing genes that may be beneficial in some unknown future.


DNA

Deoxyribonucleic acid, or DNA for short, is a long thin chemical which contains genetic instructions for the development and functions of living organisms. DNA is made up of two strands twisted together to made something called a ‘double helix’. The helix is held together by hydrogen bonds between the bases and the strands.  The part of DNA that has the genetic code for making a particular protein is called a gene. Genes can be found along thread like structures called Chromosomes. These are the packaging system of our DNA that allows 2m to fit in the nucleus of every cell. In the case of humans we have 46 distinct packages, 23 from each parent.  

Genes

Genes are an area of the DNA encoding information that can be used in the production of protein. Humans have 30,000 or so areas of coding DNA. This DNA encodes for all of the different proteins that perform all the cellular tasks in the body and also define the different traits and characteristics we all have. One example of people traits is hair colour which is inherited from parents.

Genes make such protein as;

  • Structural proteins where are found in muscles and hair
  • Enzymes such as proteases and carbohydrates.
  • Haemoglobin

Figure 1; the location and storage of DNA in the Nucleus of a cell.

Alleles

A number of the same genes are called alleles. From this you inherit one allele for each gene from your father and one allele from each gene from your mother, making all of your non-sex cells diploid. For example, the gene for eye colour has alleles for blue eye colour and alleles for brown eye colour. Your eye colour will depend on the combination of alleles you have inherited from your parents.

Figure 2; Diploid Inheritance of Genes.


Inheriting Disease:

Many diseases can be inherited throughout the family, but some are affected by their environment. These could include:

  • Climate
  • Diet
  • Physical accidents
  • Culture
  • Lifestyle.

The best way to show this is by describing the lifestyle of identical twins. For example if one twin exercised regular and ate health then they would have better way of life than one who does not.

What is a genetic disease/disorder?

A genetic disease/disorder is a condition caused by mutations in genes or chromosomes. While some diseases, such as cancer or Alzheimer’s, are due to genetic mutations acquired in a few cells during life, the term "genetic disease" most commonly refers to diseases present in all cells of the body from conception.

Two examples of inherited disorders are Cystic fibrosis and Huntingdon's diseases are;

Cystic fibrosis is a disorder that affects the lungs and wind pipe producing thick, sticky white mucus making it hard to breathe. Due to this it makes it hard to fight infections and simple illnesses like the common cold. CF is caused by a recessive allele in the body. To inherit CF you must have two copies of the faulty gene. If you only have one copy in your genes this means that you are a carrier and could pass it onto your offspring if met by another gene with the same fault. If two faulty genes are inherited there is a one in four chance that that individual’s child may inherit the disorder.

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The diagram shows who will get the CF disorder is each parent carries one faulty allele.

Figure 3; shows who will be affected from the faulty allele    

Huntington’s disorder is a disorder passed on from birth but the symptoms are not seen until middle age, which means that the disorder can’t be caught. The first symptom of the disorder is not being able to control the mussels; they soon find it hard to remember and finally after a few years the patient can’t control their movement. ...

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