Genetic engineering

Question 1

Define genetic engineering

Answer 1

The deliberate modification of the characteristics of an organism by manipulating its genetic material.

Question 2

Define transgenic

Answer 2

An organism that carries a gene from another organism

Question 3

Define vector

Answer 3

A means of inserting DNA from one organism into the cells of another organism

Question 4

Define recombinant DNA

Answer 4

DNA that contains genetic material from two sources

Question 5

Define transformation

Answer 5

The process where a plasmid with recombinant DNA must be transferred into the host cell

Question 6

Define electroporation

Answer 6

The use of a very tiny electric current to transfer genetically engineered plasmids into bacteria or to get DNA fragments directly into eukaryotic cells

Question 7

Define marker gene

Answer 7

A marker gene is a gene used to determine if a nucleic acid sequence has been successfully inserted into an organism’s DNA.

Question 8

Define DNA ligase

Answer 8

Facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

Question 9

Define sticky ends

Answer 9

An end of a DNA double helix at which a few unpaired nucleotides of one strand extend beyond the other.

Question 10

Describe the principles of genetic engineering.

Answer 10

1. The basic principles involve isolating a gene for a desirable characteristic in one organism and placing it into another organism, using a suitable vector
2. The two organisms between which the genes are transferred may be the same, similar or very different species
3. An organism that carries a gene from another organism is transgenic and is often called a genetically modified organism

Question 11

Describe 2 ways in which a desired gene can be isolated.

Answer 11

1. Using restriction enzymes

2. Using reverse transcriptase

Question 12

Describe the restriction enzyme method of isolating a desired gene

Answer 12

1. The most common technique uses enzymes called restriction endonucleases to cut the required gene form the DNA of an organism
2. Each type of endonuclease is restricted to breaking the DNA strands at specific base sequences within the molecule
3. Some make a clean blunt ended cut, but many cut the two strands unevenly leaving one of the two strands of the DNA fragment a few bases longer tan the other strand.
4. These regions with unpaired, exposed bases are called sticky ends
5. Sticky ends make it much easier to insert the desired gene into the DNA of a different organism

Question 13

Describe the reverse transcriptase enzyme method of isolating a desired gene

Answer 13

1. The other technique involves isolating the mRNA for the desired gene and using the enzyme reverse transcriptase to produce a single strand of complementary DNA.
2. This technique makes it easier to identify the desired gene, as a particular cell will make some very specific types of mRNA

Question 14

Explain how a plasmid can be used as a vector.

Answer 14

1. They are small circular molecules of DNA separate form the chromosomal DNA that can replicate independently.
2. Once a plasmid gets into a new host cell it can combine with the host DNA to form recombinant DNA

Question 15

Explain how marker genes can be used to identify organisms that have been successfully genetically engineered.

Answer 15

1. The plasmids that are used as vectors are often chosen because they contain a marker gene
2. e.g. they may have been engineered to have a gene for antibiotic resistance. This gene enables scientists to determine that the bacteria has taken up the plasmid by growing the bacteria in media containing the antibiotic.

Question 16

Describe how to insert a DNA fragment into a plasmid

Answer 16

1. First it must be cut open- use the same restriction endonuclease as used to isolate the DNA fragments as this results in the plasmid having complementary sticky ends to the sticky ends of the DNA fragment
2. Once the complementary bases of the two sticky ends are line up, the restriction enzyme DNA ligase forms phosphodiester bonds joining the two strands of DNA together.

Question 17

What is the second marker gene and how is it useful

Answer 17

1. The plasmids used as vectors are usually given a second marker gene, which is used to show that the plasmid contains the recombinant gene.
2. This marker gene is itself often placed in the plasmid by genetic engineering methods.
3. The plasmid is then cut by the restriction enzyme within this marker gene to insert the desired gene
4. If the DNA fragment is inserted successfully, the marker gene will not function
5. Gene for anitbiotic resistance used to be used but concerns about antibiotic resistance means that often genes producing fluorescence or an enzyme that causes a colour change are used

Question 18

Describe the process of culturing plasmids and bacterial cells for transferring a vector to a host cell

Answer 18

1. One method is to culture the bacterial cells and plasmids in a calcium-rich solution and increase the temperature.
2. This causes the bacterial membrane to become permeable and the plasmids can enter

Question 19

Describe the process of electroporation

Answer 19

1. A small electrical current is applied to the bacteria
2. This makes the membranes very porous and so the plasmids move into the new cells
3. Electroporation can also be used to get DNA fragments directly into eukaryotic cells.
4. This new DNA will pass through the cell membrane and the nuclear membrane to fuse with the nuclear DNA.
5. The power of the electric current needs to be carefully controlled or the membrane is permanently damaged or destroyed

Question 20

Describe the process of electrofusion for transferring a vector to a host cell

Answer 20

1. Tiny electric currents are applied to the membranes of two different cells.
2. This fuses the cell and nuclear membranes of the two different cells together to form a hybrid or polypoid cell, containing DNA from both. Used to produce GM plants
3. In animals the cells don’t fuse as effectively. Their membranes have different properties and polypoid animal cells do not usually survive in the body of a living organism
4. But electrofusion is important in the production of monoclonal antibodies.
5. A monoclonal antibody is produced by a combination of a cell producing one single type of antibody with a tumour cell, which means it divides rapidly in a culture.

Question 21

Describe how GM plant cells can be micro-propagated.

Answer 21

1. Cut the leaf
2. Expose leaf to bacteria carrying a weedkiller-resistance gene and an antibiotic resistance gene. Allow bacteria to deliver the genes into the leaf cells
3. Expose the leaf to an antibiotic to kill cells that lack the new genes. Wait for the surviving cells to multiply and form a callus
4. Allow callus to sprout shoots and roots
5. The plants are transferred to soil where they can develop into fully differentiated adult plants that are resistant

Question 22

Describe the process of using genetic engineering to produce human insulin using bacteria.

Answer 22

1. Use restriction enzymes to cut out the insulin producing gene.
2. Cut open the plasmid using the same restriction enzyme
3. This produces sticky ends which are complementary to the isolated gene
4. Base pairing of sticky ends lines up the plasmid and gene.
5. DNA ligase catalyses the formation of phosphodiester bonds joining the sugar-phosphate backbone
6. This forms a recombinant plasmid
7. Mix the recombinant plasmid with bacteria host cells by the process of transformation

Question 23

Outline the positive and negative issues relating to the genetic manipulation of microorganisms

Answer 23

Positives
1. Substances can be produced in a very large quantity
2. Used to store a living record of the DNA of another organism in DNA libraries. DNA sequencing projects enable scientists to build a collection of sequenced DNA fragments from one organism that is then stored in microorganisms through genetic engineering.
3. GM microorganisms are widely used in research for developing medical treatments and industrial processes. But pathogens are not used for health and safety reasons
Concenrns
1. Genetic engineering of pathogens could be used for the purposes of biological warfare.
2. Very little other ethical debate as have been used successfully for many years now

Question 24

Describe the benefits of, and the ethical issues concerning, insect resistance in genetically modified soya beans.

Answer 24

1. Soya beans are a major world crop
2. One modification- inserted gene so that they produce Bt protein which is toxic to many of the pest insects that attack the plant and is widely used as a pesticide by organic farmers
3. Another modification is a strain of soya beans that have been engineered so they are resistant to a common weed killer and to contain Bt protein, so farmers can spray to get rid of weeds and don’t need to use pesticides
4. This should give a higher yield with less labour and expenses.

Question 25

Name 7 useful characteristics that could potentially be genetically engineering into plants.

Answer 25

1. Pest resistance
2. Disease resistance
3. Herbicide resistance
4. Extended shelf life
5. Growing conditions
6. Nutritional value
7. Medical uses

Question 26

Describe the pros and cons of pest resistance

Answer 26

Pros:
1. Reduce amount of pesticides spraying, protecting the environment and helping poor farmers.
2. Increased yield
Cons:
1. Non-pest insecs and insect-eating predators might be damaged by the toxins in the GM plants
2. Insect pests may become resistant to pesticides in GM crops

Question 27

Describe the pros and cons of disease resistance

Answer 27

Pros:
1. Crop varieties resistant to common plant diseases can be produced, reducing crop losses/increasing yield
Cons:
1. Transferred genes might spread to wild populations and cause problems e.g superweeds

Question 28

Describe the pros and cons of herbicide resistance

Answer 28

Pros:
1. Used to reduce competing weeds and increase yield
Cons:
1. Biodiversity could be reduced if herbicides are overused to destroy weeds
2. Fears of superweeds

Question 29

Describe the pros and cons of having an extended shelf-life

Answer 29

Pros:
1. Reduces food waste
Cons:
1. May reduce commercial value and demand for the crop

Question 30

Describe the pros and cons of increasing the range of growing conditions

Answer 30

Pros:

1. Crops can grow in a wider range of conditions/survive in adverse conditions

Question 31

Describe the pros and cons of increasing the nutritional value

Answer 31

Pros:
1. Nutritional value of the crop can be increased
Cons:
1. People may be allergic to the different proteins made in GM crops

Question 32

Describe the pros and cons of using plants for medical uses

Answer 32

Pros:

1. Plants could be used to produce human medicines and vaccines

Question 33

Describe the concerns people have over patenting and technology transfer in GM crops.

Answer 33

1. Major concern is that people in less economically developed countries will be prevented from using them by patents and issues of technology transfer
2. When someone discovers a new technique they can patent it, meaning the people who most need the benefits of the characteristics may be unable to afford the seeds.
3. They also rely on harvesting seed from year to plant the next year, which patenting may make impossible

Question 34

Describe 2 examples of genetically modified farm animals for food production.

Answer 34

1. Swine fever-resistant pigs- Scientists have successfully inserted a gene from wild African pigs into the early embryos of a European pig strain giving them immunity from African swine fever
2. Faster-growing salmon- GM Atlantic salmon have received genes from faster-growing salmon. The genes cause them to produce growth hormones all year round. Grow to adult size in half the time.

Question 35

Define pharming

Answer 35

The use of genetically modified animals to produce pharmaceuticals

Question 36

Describe the two aspects to the field of pharming (including an example for each)

Answer 36

1. Creating animal models- addition or removal of genes so that animals develop certain diseases, acting as models for the development of new therapies e.g. knockout mice have genes deleted so they are more likely to develop cancer
2. Creating human proteins- introduction of a human gene coding for medically required protein. Animals are sometimes used because bacteria cannot produce all the complex proteins made by eukaryotic cells.
   e. g The human gene can be introduced to the genetic material of a fertilised cow, sheep or goat egg along with a promoter sequence so the gene is expressed only in the mammary glands. The fertilised, transgenic female embryo is then returned to the mother. A transgenic animal is born and its milk contains the desired human protein and can be harvested.

Question 37

Describe the benefits of, and the ethical issues concerning, both types of gene therapy in humans

Answer 37

Raises questions:

1. Should animals be genetically engineered to act as models of human disease?
2. Is it right to put human genes into animals?
3. Is it acceptable to put genes from one species into an animal without being certain it will not cause harm?
4. Does genetically modifying animals reduce them to commodities?
5. Is welfare compromised during the production of genetically engineered animals?