Variation - Genetic Engineering (GCSE Biology)

New 3 Genetic Engineering

Process of Genetic Engineering

Understanding Genetic Engineering

Genetic engineering involves introducing a gene from one organism into the genome of another organism to introduce desirable characteristics. Genetic engineering is also known as genetic modification. It can involve removing, changing or inserting individual genes.

Genetic engineering is a very topical discussion. Many groups are opposed to it, however others believe that it is a necessary tool for the future of science.

The Use of Bacteria

Bacteria are useful in genetic engineering because:

• They have a rapid reproduction rate
• They can make complex molecules e.g. insulin
• There aren’t many ethical concerns over their manipulation and growth
• Their genetic code is shared with all other organisms. Hence, despite genes coming from other organisms, the bacteria can still produce the same proteins.
• They have plasmids which are easy to modify and transfer.

Mechanism of Genetic Engineering

1. Select a desired phenotype – the first step is to identify the desired characteristic or phenotype we need. In this case, the desired characteristic is insulin production.

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Applications of Genetic Engineering

Genetic Engineering in Plants

Genetic engineering of crops can produce genetically modified (GM) crops.

• Improve crops – farmers can use genetic engineering to produce better crops. This will give them more money and help the consumer. They produce crops that are resistant to disease or pests like maize that has been made to be resistant to larvae of some moths as they would eat the crops. Or they produce crops that have large fruits. Crops like soya, can also be made resistant to herbicides, which means that herbicide can be used to kill the weeds, but the crop survives, aiding the yield.
• Aid humanitarian situations – crops can be genetically engineered to aid humanitarian situations by providing additional vitamins. Golden Rice was produced to be given in regions that suffered from Vitamin A deficiencies. It contains a substance called Beta-Carotene that provides its golden colour. This aided with vision problems across the world. However, due to debate over GM crops, golden rice was not produced worldwide.

Genetic Engineering in Animals

• Produce insulin – bacteria can be genetically modified to produce insulin. Before, we used to use insulin from animals (e.g. porcine and bovine insulin), but this was inefficient. Therefore bacteria have been engineered to produce insulin. Insulin is used to treat Diabetes, a condition that leads to an inability to control glucose levels in the body. Insulin produced by bacteria can be injected to treat these patients.
• Drive medical research – medical research uses genetic engineering. After the advent of using bacteria to produce insulin, there are many more avenues that are being considered through genetic modification. They are looking into ways to treat HIV, sickle cell anaemia, Huntington’s and Cystic Fibrosis.

Negatives of Genetic Engineering

Exam questions can often ask about the positives and negatives of genetic engineering. For the positives, you can use the examples from above. Here are some negatives:

• Health risks – some genetically modified foods can lead to health risks, for example they could contain chemicals that cause allergy or toxins.
• Ethical hazards – some do not believe that it is ethically fair to modify organisms and make newer life forms.
• Unknowns – there are many worries about the unknowns involved with genetically modified crops. People worry that they could lead to a huge effect on the ecology of organisms. They could lead to negative effects on the populations of wild flowers and organisms. Moreover, we do not know all of the effects of eating GM crops. There could be unforeseen consequences that we will only find out in the future. Also, there is also the concern that the genes could be passed on to weeds e.g. making them herbicide resistant.
• Costs – this could also make crops more expensive.

Using Enzymes to Isolate Genes

You can describe the steps of genetic engineering. To do this, think about the basic steps we learnt above. Genetic engineering involves removing DNA from the genome of one organism and placing it into the genome of another.

Enzymes are used in the process of removal. Here is a summary of the steps involved in isolation of the insulin gene to produce transgenic bacteria – this means that the bacteria have genes that were transferred into them from a different species:

1. The required gene is isolated by restriction endonuclease and produces ‘sticky ends’. Restriction endonuclease enzymes act as scissors, cutting the genome of the human cell and removing the insulin gene. The enzymes target specific sequences of DNA and cut the DNA here. This leaves the isolated insulin gene with ‘stick ends’ – ends with unpaired bases.

Sometimes the vector might not be transferred into the bacterium correctly. Hence, you can identify and select those cells that have successfully been modified. You can do this using antibiotic resistant markers. A gene that codes for antibiotic resistant is inserted into the plasmid at the same time as the desired gene e.g. the insulin gene. The bacteria are cultured on a plate covered with antibiotics. The cells that grow and survive will be the ones with the antibiotic resistant gene and the insulin gene.

Remember both sets of enzymes (restriction and ligase enzymes) are specific to certain base sequences.

Genes must be transferred into an organism early in development. This will allow them to spend time properly growing and gaining the characteristics that were selected.