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How we can use genes

Gene therapy

Gene therapy is a treatment that introduces DNA in a patient to treat or prevent a genetic disease. Gene therapy is still under research but the exciting possibility of treating genetic and infectious disorders is close to reality.

In most gene therapy studies, a normal gene replaces a disease-causing gene. A carrier molecule, called a vector, is used to deliver the normal gene to the patient’s target cells. The vector most commonly used is a virus, which delivers genetic material in a similar way to that it normally uses to infect human cells. The cells then produce the required proteins and are restored to their normal, functioning state.

Genes implicated in cystic fibrosis, prostate cancer and many more disorders are currently being researched. The benefits of gene therapy have to be weighed against issues such as the body’s immune reaction to introduction of foreign materials and ethical considerations such as who would receive and who would pay for this expensive form of treatment.

Click here to learn more about how gene therapy is being used to combat other diseases.

Genetic engineering

Genetic engineering is the process of altering the characteristics of an organism by changing its DNA.

This has been done on a large scale in the production of human insulin. At one time insulin for the treatment of diabetes was obtained from slaughtered cows and pigs, however, because of the slight differences from human insulin, there were problems with immune reactions and side effects. Scientists identified the human gene for the production of insulin and, using special enzymes, were able to remove it and implant it in bacterial cells.

The altered bacteria multiplied and soon millions of bacterial cells were producing human insulin. The same process was used to produce human growth hormone (previously only available from cadavers) and today many drugs and vaccines are produced in this way.

By using genetic engineering animals and plants with desired characteristics can be produced. Scientists can produce crops that will grow in previously hostile environments, fruits and vegetables that are bigger, look more appetising and stay fresh longer and animals that produce, for example, more milk, better meat or are faster growing. Such organisms are described as genetically modified (abbreviated to GM) and, although there are apparent advantages, there is much debate as to the safety and desirability of GM foods.

DNA profiling

DNA, or genetic, profiling is a procedure of analysing the DNA in samples of body tissue or fluids for the purposes of identification. DNA profiling tests the highly variable regions of a person’s DNA that contain short repeating sequences called short tandem repeats (STRs). The exact number of repeats varies from person to person. Because of genetic inheritance, DNA profiling can be used to confirm if people are closely related or not.

Police tape at the scene of a crime
Tony Webster

A sample of tissue, as small as that found at the root of a hair, is usually enough. DNA is isolated from the sample and subjected to a laboratory procedure involving various stages. The end product is a DNA profile that resembles the peaks on a graph. This can be compared to the DNA profile of tissues found at a crime scene to confirm the presence (or not) of a suspect.

Some of the additional uses for DNA profiling are:

  • identifying human remains
  • paternity testing
  • heredity studies
  • diagnosis of inherited disorders

As of 2012 the DNA database in the UK was one of the most extensive in the world with over 6 million records. This can be a very useful resource, however, there is concern that many records of individuals, who have been found innocent of crime, have been kept on the database, which is regarded by some as a breach of civil liberties.

Discussion point

DNA profiling has proved to be a useful tool for solving crimes. Since 2010 in the UK your DNA profile is taken and stored if you are arrested, even if you are not found guilty. Some argue that the DNA database intrudes on individual’s privacy. It is debated whether all individuals should have their DNA in the national database.

Do you think all individuals should have their DNA in the national DNA database?

Can you think of any ethical concerns associated with this?

Exam style questions

1. Decide whether each of the following statements about the production of insulin by genetic engineering are true or false:

a. Plasmids are found in bacterial cells.
TRUE
FALSE
TRUE
FALSE
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
b. The gene for production of insulin is placed in human DNA.
TRUE
FALSE
TRUE
(The correct answer is:
'FALSE')
FALSE
null
(The correct answer is:
'FALSE')
null
(The correct answer is:
'FALSE')
null
(The correct answer is:
'FALSE')
c. Some bacteria naturally produce insulin.
TRUE
FALSE
TRUE
(The correct answer is:
'FALSE')
FALSE
null
(The correct answer is:
'FALSE')
null
(The correct answer is:
'FALSE')
null
(The correct answer is:
'FALSE')
d. Enzymes are used to remove the human gene for insulin.
TRUE
FALSE
TRUE
FALSE
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
e. A large amount of insulin can be produced by bacteria.
TRUE
FALSE
TRUE
FALSE
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')
null
(The correct answer is:
'TRUE')

2.

Which one of the following statements about genetic engineering is true?
Genetic engineering changes all the DNA in an organism
Genetic engineering changes a specific gene in an organism
Genetic engineering changes a specific chromosome in an organism
Genetic engineering changes all the DNA in an organism
(The correct answer is:
'Genetic engineering changes a specific gene in an organism')
Genetic engineering changes a specific gene in an organism
Genetic engineering changes a specific chromosome in an organism
(The correct answer is:
'Genetic engineering changes a specific gene in an organism')
null
(The correct answer is:
'Genetic engineering changes a specific gene in an organism')
null
(The correct answer is:
'Genetic engineering changes a specific gene in an organism')

3. Study the sentences below, and select the answer from the drop down menu.

In gene therapy a normal gene replaces a defective gene.

Genetic engineering can be used to produce human insulin.

An organism that has had its DNA altered is said to be genetically modified.

In gene therapy, a carrier molecule is known as a vector .

Genetic fingerprinting can be used to identify human remains.

A DNA fingerprint is unique to an individual.