6.2.1 Cloning

Question 1

Define a clone

Answer 1

An exact genetic copy of a gene, cell or organism made by asexual reproduction

Question 2

Name 3 places clones are found naturally

Answer 2

1. Identical twins (Embryo splitting in two)
2. Asexual reproductgion in plants (Runners)
3. Asexual reproduction in bacteria (Binary Fission)

Question 3

How do genetic differences occur in asexualy reproduced organisms?

Answer 3

Mutations in DNA nucleotide sequence

Question 4

Define propagate

Answer 4

To breed speciemans (plant or animal) by natural processes from parent stock

Question 5

Why are natural reproductive clones more common in plants than animals?

Answer 5

• Plants have meristem tissue
• Plants retain the ability to differentiate (totipotent)
• Plants can de-differentiate and then differentiate into a different cell type

Question 6

What is vegetative propagation/reproductive cloning?

Answer 6

Vegetive structures develop into fully differentiaed genetically identgical plant to parent

Question 7

What is the difference between reproductive and non-reproductive cloning?

Answer 7

Reproductive cloning is the process of artificially cloning organisms whereas non-reproductive cloning is the process of making many identical copies without the intent to produce a new organism

Question 8

When is non-reproductive cloning used? (3)

Answer 8

• PCR
• Growing stem cells
• Growing tissue in culture

Question 9

Nmae parts of a plant a new clone can be propagated from (4)

Answer 9

• Stem
• Leaf
• Bud
• Root

Question 10

Name the 5 steps to taking cuttings of plants

Answer 10

1. Use a healthy shoot
2. Cut stem at a slant between the nodes
3. Dip in rooting powder containing auxin to encourage root development
4. Place in soil and add water
5. Cover with plastic bag

Question 11

Advantages of using propagation over seeds (5)

Answer 11

• Some crops can’t reproduce asexually from seeds
• Uniform and predictable size, shape and quality
• Easier to harvest
• Propagation can be completed at any time of the year
• Quicker than growing seed using sexual reproduction

Question 12

Disadvantage of using propagation over seeeds

Answer 12

Lack of genetic variation in offspring

Question 13

What is micropropagation?

Answer 13

Tissue culture where genetically identical clones are grown from explants on sterile nutrient rich jelly

Question 14

When is micropropagation used? (5)

Answer 14

When a plant:
- Doesn’t readily produce seeds
- Doesn’t respond well to natural cloning
- Is very rare
- When genetic modification hasn’t worked
- Needs to be pathogen free

Question 15

What are explants?

Answer 15

Meristematic tissue from shoot tips or lateral buds (Needs to be undifferentiated totipotent tissue)

Question 16

Explain the steps of micropropagation

Answer 16

1. Explants placed on nutrient growth medium
2. Surface of tissue cleaned using sterilising agent + aseptic technique used
3. Explansts undergo mitsosis to form a callus
4. After a few weeks callus is subdivided and placed on different nutrient medium containing cytokinins that promote shoot growth
5. Growing shoots transferred onto a different medium containing auxins to stimulate root grwoth
6. Growth medium also contains magnesium for chlorophyll production, nitrates for protein synthesis, sucrose for respiration
   7.Plantlets transferred to sterile compost to grow into small crops in a greenhouse

Question 17

What is used to clean the surface of tissue and why?

Answer 17

Sterilising agents (e.g ethanol) and aseptic technique
Prevents growth of bacteria and fungi which could compete with plant tissue

Question 18

What is a callus?

Answer 18

A mass of undifferentiated cells

Question 19

What is the role of cytokinins in micropropagation

Answer 19

Promote mitosis + stimulate shoot production - causes cells to differentiate into shoot cells

Question 20

What is the role of auxins in micropropagation

Answer 20

Promote mitosis + stimulate root growth, creating a plantlet

Question 21

What other minerals andmolecules are present in micropropagation growth medium and what are they used for? (3)

Answer 21

• Magneisum ions for chlorophyll production for photosynthesis
• Nitrate ions for protein synthesis
• Sucrose converted to glucose for respiration

Question 22

Advantages of micropropagation (7)

Answer 22

• Rapid production of large numbers of plants compared to growing from seeds
• Enables gorwing of relatively infertile seeds
• Plants will have known genetic makeup and be uniform
• Can produce disease free plants
• Can produce viable numbers of plants after genetic modification
• Produces large numbers of seedless plants
• Increases numbers of rare or endangered plants

Question 23

Disadvantages of micropropagation (6)

Answer 23

• No genetic variation
• Reduced gene pool decreases evolution chances
• Expensive process that requries skilled workers
• Explants + plantelets vulnerable to mould infection
• If source is infected with a virus, all clones will be
• Large numbers of new plants can be lost during the process

Question 24

List natural invertebrate clones (3)

Answer 24

• Starfish
• Flatworms + sponges
• Hydra

Question 25

List natural vertebrate clones

Answer 25

Identical twins (monozygotic twins)

Question 26

What are the two methods of producing artifical clones of vertebrates?

Answer 26

- Artificial twinning (splitting embryos manually) - Somati cell nuclear transfer (uses enculeated eggs)

Question 27

Explain the stages of artifical twinning in cows (4)

Answer 27

1. Cow treated with FSH hormone causing several eggs to be released (superovulated) 2. Eggs washed out of oviduct and collected 3. Eggs fertilised naturally or by artifical insemination or grown in vitro (IVF) 4. Developing embryo cells separated into smaller embryos - each goes on to produce a genetically identical organism

Question 28

How can the risks of twinned pregnancies be avoided using artifical winning?

Answer 28

Each embryo implanted into a differen surrogate mother

Question 29

What does somatic cell nuclear transfer allow the cloning of?

Answer 29

An adult animal

Question 30

Explain the 6 stages of somatic cell nuclear transfer in cows

Answer 30

1. Cow treated with FSH hormone causing several eggs to be released (superovulated) 2. Eggs washed out of oviduct and collected 3. Nucleus removed from the egg cell (Cell enucleated) 4. Nucleus removed from a differentiated somatic cell of the organism to be cloned and placed in enculeated egg cell 5. Mild electric shock given to cause fusion and to stimulate division to begin 6. Egg cell develops using genetic information from inserted nucleus so embryo develops into clone of animal cell from the somatic cell taken

Question 31

Where is the mitochondrial DNA in the new animal created from?

Answer 31

The original cow's egg cell

Question 32

Advantages of somatic cell nuclear transfer (3)

Answer 32

- Can clone pets and top race horses - Allows replication of GM embryos - Potential to reproduce rare, endangered or extinct organisms

Question 33

Disadvantages of somatic cell nuclear transfer (3)

Answer 33

- Many eggs needed to make a single cloned animal - Many cloned animals have shortened life spans - Many cloned animals fail to develop, miscarry or are deformed