Understanding Biotechnology

What is Biotechnology

Overview of Biotechnology

History of Biotechnology

Why do we do biotechnology?

Biotechnology for the environment

Biotechnology for food and agriculture

• changes in the DNA determining these features
• changes to and interactions with the environment.

Any change in our genes or DNA is called a mutation. All genetic variation has arisen from mutations. The different forms of a gene that arise through mutation are called alleles.

While we most often associate mutations with genetic diseases, much of the variation has led to a highly complex body that works extremely well in our environment.

Some mutations may change the gene so that it codes for a protein that works just as well, or maybe even better than, the protein coded for by the original gene.

Unfortunately, however, some gene changes result in the production of a different protein that does not work as efficiently, or in the same manner, as the one usually coded for by that gene. In some cases, no functional protein is produced at all. In such cases, the mutation or gene change may cause a genetic condition or disease, such as cystic fibrosis or Huntington's disease.

Approximately 3% of Australian babies may be born with a genetic condition where one or more genes that played an important role have been mutated.

For fact sheets on how genetic disorders are inherited, go to the Centre for Genetics Education. There are fact sheets on:
Autosomal recessiveness: http://www.genetics.com.au/factsheet/fs8.html
Autosomal dominance: http://www.genetics.com.au/factsheet/fs9.html
X-linked inheritance: http://www.genetics.com.au/factsheet/fs10.html

Genetic testing

Until recently, family histories were the only tools available for identifying an inherited disease. These histories can now be combined with genetic testing.

Genetic tests look at a person's genetic material: genes or DNA. Such tests can compare the base sequences in sections of DNA, look at the results of a change or mutation that is present in the DNA, or examine the shape and structure of chromosomes.

DNA is usually taken from a blood sample, but other body fluids or tissues may be used. The tests may look for predisposition to disease, or confirm a genetic mutation in an individual or family. As well as studying changes to chromosomes or genes, genetic testing also includes biochemical tests for certain proteins that indicate disease-causing gene variations.

Carrier testing can determine if a couple is ‘carrying’ a particular gene mutation for an inherited disorder (such as cystic fibrosis) that they may pass on to their children.

Predictive genetic testing focuses on tests that identify if someone will develop a disease before any symptoms appear. These tests can be useful for early detection, diagnosis, prognosis and treatment (if available).

Genetic testing is also used to identify people with an increased risk or predisposition of developing a particular condition, such as certain cancers. This information may be useful in helping to prevent, treat or manage the disease, but it also raises many issues for our community.

Looking at DNA

One method to detect changes is to cut the DNA into small fragments using restriction enzymes. The cut DNA samples are then compared with other samples from people with and without the particular mutation.

For some types of DNA tests, gene probes are used. These are short sequences of DNA that have base sequences exactly matching the gene change that is being tested for. If the altered sequence is present in a sample of a person's DNA, the probe will bind onto that piece of DNA, indicating the presence of the disease-causing gene.

Currently, gene tests are available for a number of diseases, including: cystic fibrosis, some forms of haemophilia, muscular dystrophy, Huntington's disease, thalassaemia and Tay-Sachs disease

Looking at chromosomes

In this state (called metaphase) the chromosomes can be stained, photographed and arranged for easy identification and comparison. These photographs are called karyotypes.

Sometimes, when eggs or sperm are being produced, the chromosome pairs do not separate properly. This results in an egg or sperm cell that has more or less than the usual 23 chromosomes.

If an egg or sperm carrying 24 chromosomes combines with an egg or sperm carrying the usual 23 chromosomes, the result will be an individual with cells in which there are 47 chromosomes instead of 46.

An extra copy of chromosome 21 is responsible for Down syndrome and is called Trisomy 21. An extra copy of chromosome 18 results in Edward syndrome.

For more information on genetic conditions associated with chromosomal abnormalities, go to: http://www.genetics.com.au/factsheet/index.html

Newborn screening

• phenylketonuria (PKU)
• congenital hypothyroidism
• cystic fibrosis
• other rare metabolic conditions.

All or some of the symptoms of these disorders can be prevented, or their severity reduced, if the condition is diagnosed and treated early in life. Newborn screening programs use a blood sample obtained by a heelprick from babies about three days after birth.

These blood samples are stored on a special pre-printed filter paper called a Guthrie card. Different chemicals and proteins are measured in this sample to determine whether the baby may have a particular disease. If these tests indicate that the baby may have a genetic condition such as cystic fibrosis, then their DNA may be tested to see if they carry a gene variant causing this.

This provides information to the parents if they are hoping to have more children. Guthrie cards are stored by the laboratory doing the testing. Some people have expressed concerns about how the DNA in the blood of these cards may be used in the future.

 

PKU is an inherited disorder. Affected children cannot convert phenylalanine (an amino acid commonly found in food) to tyrosine, because they lack a liver enzyme called phenylalanine hydroxylase.

If the disease is not treated with a special diet as soon as possible after birth, the child will develop severe brain damage and developmental delay. If the child is fed a special diet low in phenylalanine, development will be normal. For this reason, it is important to diagnose babies as soon as possible. PKU is one of several diseases newborn screening programs look for

Having a genetic test

• whether or not to have the test in the first place
• who to tell about the test results
• how to live your life with the information provided by the test
• how much support you need to deal with the choices you must make, and the way you may have to change your lifestyle.

Your choices may affect you and your family. To make these choices, the following need to be considered:

What does the test result mean?

Will you definitely develop the disease you’ve been tested for?

Gene tests do not always provide a definite 'yes' or 'no' answer.

Or, perhaps you have an increased risk (predisposition) for developing a disorder? This means that you have a greater chance of developing a condition than other people around you, but it may never happen. However, if you find out that you do have an increased risk, this information may enable you to more closely monitor the condition, or make lifestyle choices to help prevent its development.

Choice

For some disorders, such as Huntington disease, gene tests are available, but there is currently no treatment or cure. In these circumstances, some people may choose to know if they carry the gene, while others may not. Results from the test can help people make choices for the future if the result of the test indicates that they will develop symptoms later in life. However, some people would prefer not to know if no treatment is available.

Testing can also reveal information to prospective parents about their risk of having a child with a genetic condition. The results of such a test provide couples with information to help them make decisions about having children.

Implications

Gene tests may have far-reaching effects. Understanding the possible implications of a gene test is an important step in the process. Gene tests can identify people who carry mutations in their DNA, but are unaffected by them. The results may only matter when the person has children.

Gene tests can affect more people than the one having the test. Discovering your own genetic make-up may reveal or rely on genetic information about close relatives who do not want to know or reveal this information.

It is also possible for gene tests to inadvertently disclose family secrets involving paternity or adoption.

Genetic counsellors are specifically trained to help people through the process of genetic testing.

For more information about genetic counselling in Australia, see www.genetics.com.au or http://www.genetichealthvic.net.au

Who would you have to tell?

If you had a genetic test, would you have to tell your employer? Your health insurance company? Your parents? Your children?

Over two years, community consultation sessions were held by the Australian Law Reform Commission (ALRC) and the Australian Health Ethics Committee on these issues. From this public inquiry, a report on genetic testing and personal privacy was produced and presented to Parliament.

The report covers a number of topics, including how to regulate genetic privacy, discrimination and the use of genetic testing and information in employment.