Topic 4 – Natural Selection and Genetic Modification- Changing Genes

Question 1

What is selective breeding?

Answer 1

The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes

Question 2

Outline the main steps involved in selective breeding

Answer 2

1. Identify a desired characteristic e.g. disease resistance
2. Select parent organisms that show the desired traits and breed them together
3. Select offspring with the desired traits and breed them together
4. Process repeated until all offspring have the desired traits

Question 3

what is the main advantage of selective breeding

Answer 3

Creates organisms with desirable features.
crops produce higher yield of grain
cows produce greater supply of milk
plant produces larger fruit
domesticated animals

Question 4

Other than in agriculture, where else is selective breeding useful?

Answer 4

In medical research

In sports e.g. horse racing

Question 5

Outline the disadvantages of selective breeding (4)

Answer 5

Reduction in the gene pool (which becomes especially harmful if sudden environmental change occurs) Inbreeding results in genetic disorders
Development of other physical problems e.g. respiratory problems in bulldogs
Potential to unknowingly select harmful recessive alleles

Question 6

How can plants be cloned?

Answer 6

Taking plant cuttings

Tissue culture

Question 7

What is tissue culture?

Answer 7

A method of growing living tissue in a suitable medium.

Question 8

Describe how plants are grown using tissue culture (biology only)

Answer 8

1. Select a plant that shows desired characteristics
2. Cut multiple small sample pieces from meristem tissue
3. Grow in a petri dish containing growth medium
4. Transfer to compost for further growth

Question 9

What must be ensured when preparing tissue cultures? (biology only)

Answer 9

Ensure aseptic conditions to prevent contamination by microorganisms

Question 10

What does the growth medium contain? (biology only)

Answer 10

nutrients and growth hormones

Question 11

What are the advantages of growing plants by tissue culture?

Answer 11

Fast and simple process
Requires little space
Enables the growth of many plant clones with the same desirable characteristics
Useful in the preservation of endangered plant species

Question 12

What are the disadvantages of growing plants by tissue culture?

Answer 12

Plant clones often have a low survival rate
Could unknowingly increase the presence of harmful recessive alleles
reduction in gene pool

Question 13

Why is animal tissue culturing useful?

Answer 13

Useful in the preparation of tissue samples for medical research
Enables the investigation of how different factors may affect a specific animal tissue, without harming the animal itself

Question 14

Describe how animal tissue cultures are prepared

Answer 14

1. Extract a sample of tissue from an animal
2. Use enzymes to separate cells within the sample
3. Grow in a culture vessel containing growth medium
4. Once grown, store the sample

Question 15

What is genetic engineering?

Answer 15

The modification of the genome of an organism by the insertion of a desired gene from another organism
Enables the formation of an organism with beneficial characteristics

Question 16

Describe the process of genetic engineering

Answer 16

1. DNA is cut at specific base sequences by restriction enzymes to create sticky ends
2. Vector DNA cut using the same restriction enzymes to create complementary sticky ends
3. Ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DNA
4. Recombinant DNA mixed with and ‘taken up’ by target cells

Question 17

What is a vector?

Answer 17

A structure that delivers the desired gene into the recipient cell e.g. plasmids, viruses

Question 18

Describe the benefits of genetic engineering (3)

Answer 18

Increased crop yields for growing population e.g. herbicide-resistance, disease-resistance
Useful in medicine e.g. insulin-producing bacteria, anti-thrombin in goat milk
GM crops produce scarce resources e.g. GM golden rice produces beta-carotene (source of vitamin A in the body)

Question 19

Describe the risks of genetic engineering (4)

Answer 19

Long-term effects of consumption of GM crops unknown
Negative environmental impacts e.g. reduction in biodiversity, impact on food chain, contamination of non-GM crops forming ‘superweeds’
Late-onset health problems in GM animals
GM seeds are expensive. LEDCs may be unable to afford them or may become dependent on businesses that sell them.

Question 20

What is Bacillus thuringiensis (Bt)?

Answer 20

Insect larvae are harmful to crops

Bt is a bacterium which secretes a toxin that kills insect larvae

Question 21

How is genetic engineering used to protect crops against insects? (biology only)

Answer 21

The gene for toxin production in Bt can be isolated and inserted into the DNA of crops
Bt crops now secrete the toxin which kills any insect larvae that feed on it

Question 22

What are the benefits of Bt crops? (3) (biology only)

Answer 22

Increased crop yields (fewer crops damaged)
Lessens the need for artificial insecticides
Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it

Question 23

What are the risks of Bt crops? (3)

Answer 23

● Long term effects of consumption of Bt crops unknown
● Insect larvae may become resistant to the Bt toxin
● Killing insect larvae reduces biodiversity

Question 24

Outline the agricultural methods of increasing food production (2)

Answer 24

● Intensive farming methods e.g. ‘battery’ farming and the use of fertilisers and pesticides
● Biological control

Question 25

What is the main advantage of intensive farming? (biology only)

Answer 25

increases crop yield

Question 26

What are the disadvantages of intensive farming methods? (3) (biology only)

Answer 26

Fertilisers can wash into nearby water sources and cause eutrophication
The use of herbicides and insecticides reduces biodiversity
‘Battery’ farming is often seen as unethical

Question 27

What is biological control? (biology only)

Answer 27

When a new organism (often a predator) is introduced into an ecosystem to control a pest or pathogen

Question 28

What are the advantages of using biological control to increase food production?

Answer 28

The results of biological control generally last for a long period of time
The effects on wildlife are less severe

Question 29

What is the risk of using biological control?

Answer 29

Risk of the control organism becoming a pest itself