T4- Changing Genes

Question 1

What is selective breeding

Answer 1

The process by which humans artificially select orgainsms 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. Selective 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 a higher yield of grain
• cows produce a greater supply of milk
• plants produce larger fruit
• domesticated animals

Question 4

Other han agriculture , where else is selective breeding useful

Answer 4

• in medical research

- in sports e.g horse racing

Question 5

Outline 4 disadvantages of selective breeding

Answer 5

• Reduction in the variation (which becomes especially harmful in sudden enviromental change)
• inbreeding results in genetic disorders
• development of other physical problams e.g respiratory problems in bulldogs
• potential to unknowingly selective harmul recessive alleles

Question 6

How can plants be cloned (2)

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

4 steps to how plants are grown using tissue culture

Answer 8

1. Select a plant that shows desired characteristics
2. Cut simple 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

Answer 9

Ensure aseptic conditions to prevent contamination by microorganisms

Question 10

What does the growth medium contain

Answer 10

Nutrients and growth hormones

Question 11

4 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 endangred plant species

Question 12

What are the disadvantages of growing plants by tissue culture (2)

Answer 12

• Reduction in the gene pool (variation)
• plant clones often have a low survival rate
• could unknowingly increase the presence of harmful recessive alleles

Question 13

Why is animal tissue culturing useful

Answer 13

• Useful in the preparation of tissue samples for medical research
• enables the investiagton of how different factors may affect a specific animal tissue

Question 14

Describe how animal tissue cultures are prepared

Answer 14

1. Extract a sample of tissue from an animal
2. Use enzymes to seperate 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

Descibe 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 using the same restirction enzymes to create complementary sticky ends
3. Ligase enzymes join the sticky ends of the DNA and vector dna forming recombinant dn
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
• GM crops produce scarce resources - e.g source if vitamin A

Question 19

Describe 4 risks of genetically engineering

Answer 19

• Long term effects of consumption of GM crops unkown
• negative envirmental impacts e.g reduction on biodiversity - impact on food chain
• Late onset health problems in GM animals
• GM seeds are expensive

Question 20

What is Bacillus thuringiensis

Answer 20

Insect larvae harmful to crops

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

Question 21

How is genetic engineering used to protect crops against insects

Answer 21

The gene for toxin production in bt can be isolated and inserted into the dna of crops
- bt crops nowsecrete the toxin which kills any insect larvae that feed on it

Question 22

Benefits of bt crops (3)

Answer 22

• Increased crop yield (fewer crops damaged)
• lessens the need for artificial insecticides
• bt toxin is specific to certain insect larvae so so is not harmful to other organsims that ingest it

Question 23

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 insext larvae reduces biodiversity

Question 24

Outline the agricultural methods of increasing food production (2)

Answer 24

• intensive farming methods e.g. use of fertilisers and pesticides
• biological control

Question 25

Main advantag of intensive farming

Answer 25

Increases crop yields

Question 26

3 disadvantages of intensive farming methods

Answer 26

• fertilisers can wash into nearby water sources and cause eutrophication
• the use of herbicides and insecticides reduces biodiversity

Question 27

What is biological control

Answer 27

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

Question 28

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

Risk of using biological control

Answer 29

Risk of the control organism becoming a pest itself