GENETIC SELECTION > INFORMATION > SHEET 3

NEW GENETICS

An understanding of the science behind modern genetics underpins an informed debate on the subject. Teachers and students will have various levels of knowledge at the beginning of The Gift. It is important that they are able to base their discussions and further work on accurate information. This section aims to outline some of the science that makes genetics so relevant to young people. While teachers will find this section provides some background information, a number of other resources are suggested in the References section that give a more in-depth view of material relevant to students. The advances in genetic science and technology result from research since the 1950s when the structure of DNA was discovered. Recently, the pace of this progress has increased tremendously. A variety of terms are frequently used to describe this science: ‘biotechnology’, ‘recombinant DNA technology’, ‘DNA science’ and ‘gene technology’. While some of these terms refer to specific aspects of the science, they are often used interchangeably. Here, we will simply refer to these techniques as the ‘New Genetics’. Dramatic Genetics aims to help young people in making informed decisions about how these advances will change their lives. New Genetics is already making an impact on all our lives. Future advances, while difficult to predict, will mean that genetics is even more relevant to this generation of students.

Cloning DNA

Being able to change and modify DNA is central to the New Genetics. In the early 1970s it became possible to genetically manipulate DNA in the laboratory, but outside the cell. This involves using biological ‘scissors’ and ‘glue’ to create new
sequences of DNA which are not found in the natural environment. DNA manipulated in this way can be introduced back into organisms where it is copied and functions alongside the host organism’s DNA. This break-through allowed the combination of genes from quite dissimilar organisms.

What is a genetic test?

In The Gift, several of the characters consider or undergo genetic tests. Genetic differences between individuals can now be directly detected. Most human body cells contain 23 pairs of chromosomes that carry genes coded in a sequence of DNA. In genetic conditions such as Down’s syndrome an extra copy of one chromosome can be seen under a microscope when the cells have been specially prepared. Genetic conditions result from mistakes that occur during the production of sex cells (which form sperm or eggs). In some cases, large parts of chromosomes may be ‘shuffled’ so that the resulting chromosomes no longer contain the correct genetic blueprint. Rearrangements can result in a piece of one chromosome being missing, being repeated or even moved to a different chromosome altogether. These changes can also be detected by examining specially prepared chromosomes under a microscope. Genetic conditions can result from even small differences in an individual’s genetic make-up. Just one change in the sequence of DNA ‘letters’ can result in a gene not being able to work properly. If the actual gene that is associated with a condition is known in detail, then it may be possible to detect such small changes. However different changes in the gene may be found in different families. In these cases reliable diagnosis depends on undertaking a combination of tests to look at each possible mistake in the DNA that could lead to disease.

For many conditions, such as Friedreich’s ataxia, the exact gene involved remains undiscovered. However, genetic testing often remains possible. Using a number of techniques, DNA markers close to where the gene is believed to be can be examined. In most cases these will be inherited at the same time as the version of the gene that causes disease. This is often only possible within family groups that have a history of the genetic disorder. For instance, no genetic test is available to confirm someone like ANNIE as having the rogue gene for Friedreich’s ataxia.

	Jennifer and Ryan Kaye

However, once her diagnosis was confirmed by examining the DNA markers from several family members, it was then possible to test her brother’s genetic status.

How did Jennifer and Ryan select Mark?

It is possible to detect some genetic disorders in embryos in the laboratory. For some years in vitro fertilization has been used by couples unable to conceive normally, but who produce healthy sperm and eggs. The mother’s egg is fertilized in the laboratory and then put back into the mother where it develops in the normal fashion. Embryos can be checked for genetic disorders, such as cystic fibrosis, before they are put back into the mother. This highly specialised technique involves removing one cell from an embryo just a few days old. The remaining cells will develop normally if it is decided to implant this embryo back into the mother. The amount of DNA that can be extracted from the removed cell is too small for conventional genetic testing: the DNA must first be ‘photocopied’ many times to give enough to carry out the tests.

	DNA Sequence

In 2010, JENNIFER and RYAN decide to use similar ‘test-tube baby’ techniques (known as pre-implantation diagnosis) to select an embryo that would not have Friedreich’s ataxia. They decide to ensure that the child (MARK) will not even be a carrier for this disorder. In addition to using these techniques to ensure that MARK is not affected by disease, RYAN selects for characteristics that he believed would be favourable. These include such characteristics as sporting ability. Such abilities are certainly not influenced by just one gene, but it is a possibility that several genes influencing sporting prowess will have been identified in 2010 as a result of the Human Genome Project.

Medicines by genetic engineering

The New Genetics is already making an impact on medical treatments. One of the clearest ways has been in the ability to produce therapeutic drugs by cloning genes. These drugs are useful in treating a variety of illnesses, including some
that have an inherited element to them.

Each year about 50 children are born with a type of dwarfism caused by a failure of the brain to produce sufficient quantities of a chemical, Human Growth Hormone (HGH). Untreated children never grow to a normal adult height. Until the 1980s these children could only be treated with HGH extracted from the brains of people who had died. There are a number of problems with this treatment - only tiny amounts of HGH could be extracted from the brains of people who had died and hence only a few children could be treated. In addition, it is now apparent that the extracted HGH could contain impurities that could increase the risk of children contracting a fatal brain disease. Genetic engineering has enabled HGH to be produced in large quantities using bacteria. All children affected can now be treated with the artificial version of HGH that does not carry the risk of transmitting infectious diseases.

Similar techniques have allowed the large scale production of human insulin for the treatment of diabetes. Previously, patients were treated with insulin derived from animals such as pigs or horses. The genetically engineered version of insulin is practically identical to the insulin a healthy person produces. A number of other products have been produced in a similar fashion including blood factors and interferon, which is used to treat some cancers.