21 Biotechnology and genetic modification

Question 1

Biotechnology

Answer 1

The exploitation of biological processes by humans for industrial and other purposes.

Question 2

Genetic engineering

Answer 2

Changing the genetic material of an organism by removing, changing or inserting individual genes.

Question 3

Why are bacteria useful?

Answer 3

Bacteria are useful in biotechnology and genetic engineering because:

they reproduce rapidly
they can make complex molecules, such as vitamin B12 and insulin.

Question 4

Plasmids

Answer 4

A short loop of DNA found in bacteria that is not part of the bacteria’s chromosome.

Plasmids naturally pass from one bacterial cell to another.
In genetic modification, a gene for a protein can be inserted into a plasmid; this gene will then be transferred to the genetic material of a bacterial cell.
The bacterial cell containing the plasmid will then express the gene and make the required protein

Question 5

Yeast

Answer 5

Yeast cells obtain their energy by anaerobic respiration. This consists of the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.

glucose → alcohol + carbon dioxide
C6 H12O6 → 2C2H5OH + 2CO2

This process is often called fermentation. The alcohol produced can be used to make biofuels, and the carbon dioxide can be used in bread-making.

Question 6

Ethanol and bread making from yeast

Answer 6

The alcohol produced by yeast is called ethanol. Ethanol can be made industrially by reacting ethene with steam at high temperatures and pressures, but the use of yeast allows it to be made at around 30 °C and normal pressure.

The yeast initially releases energy by aerobic respiration.
This produces carbon dioxide (and water), which causes the bread to rise.
Once the oxygen in the dough is used up, anaerobic respiration can take place.
The carbon dioxide produced continues to cause the bread to rise.
The ethanol released into the dough boils away when the bread is baked in the oven.

Question 7

Using enzymes

Answer 7

The use of enzymes is a common in many industries. For example, enzymes are used in:

Using pectinase in fruit juice production
biological washing powders.
the production of lactose-free milk.

Question 8

Using pectinase in fruit juice production

Answer 8

Pectin is a protein that holds cell walls together. Pectinase is an enzyme produced by the fungus Aspergillus niger. It breaks down the pectin molecules, so that the cell walls fall apart and opening up the cells so allowing juice to be extracted more easily. An additional benefit is that the juice looks clearer.

Question 9

Using enzymes in biological washing powder

Answer 9

‘Biological’ washing powders contain enzymes to digest (break down) the substances in fabric stains.

Question 10

Lactose-free milk

Answer 10

Lactase is used to produce lactose-free milk. The lactase is mixed with an alginate gel, making alginate beads that immobilise (trap) the enzyme.
By immobilising the lactase, it is possible to use it repeatedly because it is not washed away with the product.

The milk is passed through a mesh that contains the immobilised enzyme of alginate beads for several cycles until no more lactose is detected

Question 11

Large-scale production using fermenters

Answer 11

A fermenter is designed to optimize the growth of a microorganism such as bacteria.
Stainless steel structure with a water jacket to maintain temperature
Nutrients and oxygen are given to fuel the growth
Waste products of respiration, such as carbon dioxide, must be removed from the fermenter
Optimal temperature and pH at which it will reproduce quickly.
Air or substance entering the fermenter is sterilised

Question 12

Producing penicillin

Answer 12

Penicillin is an antibiotic used to control bacterial infections. It kills susceptible bacteria or prevents their growth by disrupting the production of the bacterial cell wall. This weakens the bacteria and causes them to burst when they divide.

Penicillin is produced in a fermenter.
A solution containing sucrose is added to the tank containing Penicillium .

The pH of the solution is tightly controlled by adding either acid or alkali.
The temperature of the fermenter is also controlled so the fungus is always at the optimal temperature for reproduction.
The fermenter stirs the mixture continuously to distribute the nutrients and to allow sufficient oxygen to enter.

As the Penicillium grows, it releases penicillin into its surroundings. The antibiotic is harvested in fractions of about 20–30% of the fermenter’s capacity. This partial harvesting is carried out several times to maintain a high yield.

Question 13

Mycoprotein
Insulin

Answer 13

Fermenters can also be used to grow the fungus Fusarium venenatum , which makes mycoprotein.

Fermenters are also use to produce insulin for diabetic patients using genetically engineered bacteria. The insulin produced is much higher in quality, reducing the amount of dangerous side-effects experienced by patients.

Question 14

Human protein production

Answer 14

Human genes can be inserted into bacteria to produce human proteins such as insulin.
This protein is used to treat people with type 1 diabetes.
The use of genetically modified insulin reduces the need to use insulin extracted from animals, and is tolerated better by people with diabetes.

Question 15

Herbicide resistance

Answer 15

It is possible to insert genes into crop plants that give them a resistance to a herbicide.

The herbicide can be used where the herbicide-resistant plants are growing.
The herbicide-resistant plants are not killed but the weeds are.
This means that farmers can reduce the amount of herbicide they use, and the reduced competition with weeds increases the crop yield.

However, these plants are not resistant to other herbicides, so they are only useful where the particular herbicide is used.

Question 16

Resistance to insect pests

Answer 16

It is possible to insert genes into crop plants that give them a resistance to insect pests.

One of the most well-known examples of pesticide-resistant plants is Bt corn.

Bt corn is maize that contains the gene for insect resistance from a soil bacterium called Bacillus thuringiensis (Bt).

It is an efficient insecticide that targets some insects but not others. The Bt protein does not affect mammals, fish or birds.

Question 17

Food with improved nutritional qualities

Answer 17

The nutritional quality of crop plants can be improved by increasing their vitamin and amino acid contents.

Feed crops for livestock have been genetically modified to have an increased amount of the amino acid lysine.

Beta-carotene is needed for the body to make vitamin A.
It is possible to insert genes into crop plants that make them produce large amounts of beta-carotene.
Golden rice is a genetically modified strain of rice that produces extra beta-carotene in its grains
Golden rice has helped to reduce blindness and death in children in many impoverished communities around the world.

Question 18

The main steps in genetic modification are:

Answer 18

1. Isolating the section of DNA that makes up the required human gene.
2. Cutting the DNA of a bacterial plasmid.
3. Inserting the human DNA into the plasmid DNA.
4. Inserting the plasmid into bacteria.
5. Allowing the genetically modified bacteria to express the gene and make the human protein.

Question 19

Enzymes in genetic modification

Answer 19

Steps 1 and 2 need restriction enzymes.
These enzymes cut DNA at particular places.
The two cut ends form short lengths of single-stranded DNA, which are called sticky ends.
One end contains a sequence of DNA bases that is complementary to the sequence of bases at the other end.
Steps 1 and 2 need the same restriction enzyme to ensure that the sticky ends can re-join.

Step 3 needs ligase enzymes. These enzymes join sticky ends together to make a complete length of double-stranded DNA.

Question 20

Selection of modified bacteria

Answer 20

In genetic modification, the plasmid that has been changed by the insertion of a gene is called a recombinant plasmid to some.
The genetically modified bacteria are told apart using markers for antibiotic resistance.

Before the desired gene is inserted into the plasmid, a gene for antibiotic resistance is joined to it. This means that recombinant plasmids formed at this step will carry genes for insulin and for antibiotic resistance. Any bacterium that receives one of these plasmids will now be resistant to the antibiotic. In the presence of the antibiotic, only the genetically modified bacteria will reproduce.