Genetic engineering techniques

Recently, we have begun to learn how to take evolution into our own hands through genetic engineering, which involves altering or manipulating an organism's genome to create a new and useful result. The methods often used by genetic engineers are many and varied, but generally fall under one of three categories: the plasmid method, the vector method, and the biolistic method.

The Plasmid Method

The first technique of genetic engineering, the plasmid method, is the most familiar technique of the three, and is generally used for altering microorganisms such as bacteria. In the plasmid method, a small ring of DNA called a plasmid (generally found in bacteria) is placed in a container with special restriction enzymes that cut the DNA at a certain recognizable sequence. The same enzyme is then used to treat the DNA sequence to be engineered into the bacteria; this procedure creates "sticky ends" that will fuse together if given the opportunity.

Next, the two separate cut-up DNA sequences are introduced into the same container, where the sticky ends allow them to fuse, thus forming a ring of DNA with additional content. New enzymes are added to help cement the new linkages, and the culture is then separated by molecular weight. Those molecules that weigh the most have successfully incorporated the new DNA, and they are to be preserved.

The next step involves adding the newly formed plasmids to a culture of live bacteria with known genomes, some of which will take up the free-floating plasmids and begin to express them. In general, the DNA introduced into the plasmid will include not only instructions for making a protein, but also antibiotic-resistance genes. These resistance genes can then be used to separate the bacteria which have taken up the plasmid from those that have not. The scientist simply adds the appropriate antibiotic, and the survivors are virtually guaranteed (barring spontaneous mutations) to possess the new genes.

Next, the scientist allows the successfully altered bacteria to grow and reproduce. They can now be used in experiments or put to work in industry. Furthermore, the bacteria can be allowed to evolve on their own, with a "selection pressure" provided by the scientist for producing more protein. Because of the power of natural selection, the bacteria produced after many generations will outperform the best of the early generations.

Many people strongly object to the plasmid method of genetic engineering because they fear that when the engineered plasmids are transferred into other bacteria it will cause problems if they express the gene. Lateral gene transfer of this type is indeed quite common in bacteria, but in general the bacteria engineered by this method do not come in contact with natural bacteria except in controlled laboratory conditions. Those bacteria that will be used in the wild - for example, those that could clean up oil spills - are generally released for a specific purpose and in a specific area, and they are carefully supervised by scientists.

The Vector Method

The second method of genetic engineering is called the vector method. It is similar to the plasmid method, but its products are inserted directly into the genome via a viral vector. The preliminary steps are almost exactly the same: cut the viral DNA and the DNA to be inserted with the same enzyme, combine the two DNA sequences, and separate those that fuse successfully. The only major difference is that portions of the viral DNA, such as those that cause its virulence, must first be removed or the organism to be re-engineered would become ill. This does yield an advantage - removal of large portions of the viral genome allows additional "space" in which to insert new genes.

Once the new viral genomes have been created, they will synthesize protein coats and then reproduce. Then the viruses are released into the target organism or a specific cellular subset (for example, they may be released into a bacterium via a bacteriophage, or into human lung cells as is hoped can be done for cystic fibrosis patients). The virus infects the target cells, inserting its genome - with the newly engineered portion - into the genome of the target cell, which then begins to express the new sequence.

With vectors as well, marker genes such as genes for antibiotic resistance are often used, giving scientists the ability to test for successful uptake and expression of the new genes. Once again, the engineered organisms can then be used in experiments or in industry. This technique is also being studied as a possible way to cure genetic diseases.

Many people object to this type of genetic engineering as well, citing the unpredictability of the insertion of the new DNA. This could interfere with existing genes' function. In addition, many people are uncomfortable with the idea of deliberately infecting someone with a virus, even a disabled one.

The Biolistic Method

The biolistic method, also known as the gene-gun method, is a technique that is most commonly used in engineering plants - for example, when trying to add pesticide resistance to a crop. In this technique, pellets of metal (usually tungsten) coated with the desirable DNA are fired at plant cells. Those cells that take up the DNA (again, this is confirmed with a marker gene) are then allowed to grow into new plants, and may also be cloned to produce more genetically identical crop. Though this technique has less finesse than the others, it has proven quite effective in plant engineering.

Objections to this method arise for many of the same reasons: the DNA could be inserted in a working gene, and the newly inserted gene might be transferred to wild plants. Additionally, this technique is commonly opposed because of its association with genetically modified foods, which many people dislike.

Reading Comprehension

Read the article carefully and decide if the following statements are true (T), false (F) or not stated (NS). Find in the article the sentences that can prove the true statements and correct the false statements.

1) The widely-spread technique of Genetic Engineering is the vector method.

2) A plasmid is a small ring of DNA.

3) The final step of plasmid method is when the altered bacteria grow and reproduce.

4) The molecules with the least weight have to be preserved after the successful incorporation the new DNA in one of the stages of plasmid method.

5) The plasmid with the introduced DNA includes instructions for making protein but doesn’t’ have antibiotic-resistance genes.

6) The successfully altered bacteria grow, reproduce and used in experiment and industry.

7) There are many objections to plasmid method because of ethical issues.

8) The vector method is entirely different from the plasmid method, but its preliminary steps are similar to the vector method.

9) In accordance with the vector method technique, if certain portions of the viral DNA are not removed from the organism, it will become ill.

10) The vector method has been successfully applied to cure genetic diseases.

11) People are opposed to this method because it can lead to some virus diseases,

12) The biolistic method is used in agribusinesses.

13) The biolistic method is supported by many people for many reasons.

Language Development

ǃ The Future Tenses

For predictions and general statements about the future will or will be doing are used.

Look at these sentences from the article and underline the future forms of the verb: The next step involves adding the newly formed plasmids to a culture of live bacteria with known genomes, some of which will take up the free-floating plasmids and begin to express them.

In general, the DNA introduced into the plasmid will include not only instructions for making a protein, but also antibiotic-resistance genes.

Remember that will is not normally used in a clause following a time conjunction: when, if, until, before, after, while, provided, as soon as, once, by the time etc

Once the new viral genomes have been created, they will synthesize protein coats and then reproduce.

Many people strongly object to the plasmid method of genetic engineering because they fear that when the engineered plasmids will be transferred into other bacteria it will cause problems if they express the gene.

For more information refer to English Grammar in Use by R.Murphy Un.6, 7, 9

1. Complete the sentences with a verb adding will if it is needed.

PROVIDE BECOME BE PERFECTED POLLINATE IMPROVE DEPEND BE BE RESTORED DEVELOP PRACTICE TELL COMPLETE

1. The precise nature of the future society in regards to the look of its members ____________________ on an unpredictable factor - the relative success of different development approaches.

2. It is clear that virtual reality, cyborgisation and genetic engineering all _________ ______________ almost unlimited possibilities for human expression. But which of the three methods ___________ more popular (at certain point) is hard to predict, because it depends on which one will be more advanced, more efficient, safer, cheaper, more available, easier to use, etc

3. Once this research_____________ and scientists understand each step in the life cycle of plants and animals, and once computers _________ powerful enough to simulate the consequences of any changes to DNA, then humans will be able to safely engineer almost any imaginable type of plant or animal.

4. If the tools and techniques __________ and all of the problems associated with food production can be solved, the world environment __________, and our human health and lifestyle ___________ beyond imagination.

5. If super-plants cross ____________ with weeds, will we get super-weeds?

6. If we ___________ super intelligent species or machines that are smarter than human beings, will we be replaced?

7. Only if humanity _______________ practice extremely stringent methods of preventing these technologies from getting out of control, it will be guaranteed a future. Either way, these news reports rightfully predict that these new technologies are the future, unavoidable, somewhat unpredictable, and everyone should heavily invest in the companies researching these technologies to make a small fortune. Only time ___________ who is right.

2. Find and learn Russian equivalents for the following words and expressions:

1)restriction enzymes	a)
2)to fuse together	b)
3)to weigh	c)
4)free-floating plasmids	d)
5)to possess the new genes	e)
6)to put to work in industry	f)
7)to express the gene	g)
8)lateral gene transfer	h)
9)in the wild	i)
10)to yield an advantage	j)

3. Find and learn English equivalents for the following words and expressions:

1) cеквенирование ДНК	a)
2) новые соединения	b)
3) молекулярная масса	c)
4) гены, устойчивые к антибиотику	d)
5) возражать	e)
6) исключая спонтанные мутации	f)
7) сталкиваться с	g)
8) вирусная ДНК	h)
9) непредсказуемость	i)
10) быть против, возражать	j)