Cloning and Biotechnology

Question 1

Define ‘clone’

Answer 1

• Offspring, produced by mitosis, that is genetically identical to the parent plant [organism].

Question 2

Define ‘asexual reproduction’

Answer 2

The generation of new individuals, often naturally, using mitosis to produce clones.

Question 3

Define ‘reproductive cloning’

Answer 3

• Using artificial cloning methods to procure 2 or more individuals that are clones of each other.

Question 4

Define ‘vegetative propagation’

Answer 4

The production of plant clones from non-reproductive tissues.

Question 5

Define ‘penetrating organ’

Answer 5

• Plant structures which allow them to survive adverse conditions. They constrain stored food and can remain dormant in the soil.

Question 6

Describe the link between perennating organs and vegetative propagation.

Answer 6

Vegetative propagation takes place from perennating organs after adverse conditions when they stop being dormant and the stores of food are sued to grow new plants from the organ.

Question 7

Describe 4 ways in which plants naturally clone.

Answer 7

1. Rhizomes: Horizontal underground stems.
2. Stolons: Horizontal above ground stems.
3. Tubers: Swollen underground stems.
4. Bulbs: Swollen, tightly packed, underground leaved.

Question 8

Define ‘horiculture’

Answer 8

The branch of agriculture that deals with just plants.

Question 9

Define ‘agriculture’

Answer 9

The cultivation and breeding of animals, plants, and fungi for food or other resources.

Question 10

Describe how the production of natural clones is exploited in horiculture.

Answer 10

Creating new plants by splitting up bulbs, removing young plants from runners, and cutting up rhizomes.

Increases plant numbers cheaply and all have same genetics as parents — known as ‘favoured characteristics’.

Question 11

Define ‘taking cuttings’ and describe how the process is used in horiculture.

Answer 11

• Removing and planting short sections of the stem of a plant in order to produce clones of that plant.
• Used to increase plant numbers (quicker than growing from seed).
• All clones of parents — good stock so will crop well.

Question 12

Describe 6 ways in which the success rate of of cuttings can be increased.

Answer 12

1. Using a non-flowering stem: Resources not needed to maintain cells of flowers so can be used to grow roots.
2. Make an oblique cut in the stem: Larger surface area for roots to grow from.
3. Use hormone rooting powder: Encourages the growth of new roots.
4. Reduce leaves to two or four: Reduces surface area so reduces transpiration rate as water uptake is very low until new roots are well developed.
5. Keep cuttings well watered: Will die if not enough water and needs to establish roots before it can draw enough up itself.
6. Cover the cutting with a plastic bad for a few days: Reduces loss of water while new roots establish.

Question 13

Give 5 examples of crops that are propagated by cloning.

Answer 13

1. Sugar cane
2. Bananas
3. Sweet potatoes
4. Cassava
5. Tea

Question 14

Describe the advantage of propagating crops by cloning.

Answer 14

• Large number of new plants especially of sterile plants such as seedless grapes which pleases consumers.
• Reliably increasing numbers of rare plants and/or plants difficult to grow from seed.
• Allows stocks to be built up quickly.
• Knows genetic profile so known to produce good quality crops.
• Uniform plants make harvesting easier and produces uniform quality crops.

Question 15

Describe the disadvantage of propagating crops by cloning.

Answer 15

• Produces a monoculture — all plants are susceptible to the same diseases or changes in growing conditions.
• Labour intensive
• Pathogens can be passed from parents.

Question 16

Compare production of new individuals by seed with producing new individuals by taking cuttings.

Answer 16

Seed pros:
- Genetically diverse
- Low cost
- Favoured when the genetic diversity and low cost are important.
- Occurs naturally so no need for human intervention.

Seed cons:
- Long growing time
- Need to maximise pollination and provide ideal requirements for germination and seedling growth.
- Problems occur when plants are difficult to grow from seeds e.g. orchids.

Cuttings pros:
- Clones of parents
- Short growing time
- Favoured when need good crops quickly and when plant has a high success rate for cutting/clones are wanted.
- Guaranteed quality

Cuttings cons:
- High cost/labour requirements
- Need to use non-flowering stems and rooting hormone with plenty of watering.
- Problems occur as they are susceptible to drying out.
- Pathogens can be transferred.
- Monoculture

Question 17

Define ‘tissue culture’

Answer 17

The method of growing plant cells, in isolation from the parent plant under sterile conditions in/on a nutrient culture medium of known composition.

Question 18

Define ‘micropropagation’

Answer 18

The process of making large numbers of genetically identical offspring from a single parent plant using tissue culture techniques.

Question 19

Define ‘explant’

Answer 19

The material removed from parent plant for tissue culture.

Question 20

Define ‘callus’

Answer 20

A mass of undifferentiated plant cells that has been grown from an explant.

Question 21

Describe 5 reasons why micropropagation might be used to clone plants.

Answer 21

1. The desirable plant does not readily produce seeds — sexual reproduction isn’t feasible so micropropgation is an alternative.
2. The desirable plant doesn’t respond well to natural cloning.
3. The desirable plant is very rare.
4. The desirable plant has been genetically modified or selectively bred with difficulty — produced viable numbers of identical plants.
5. The desired plant is required to be ‘pathogen-free’ — grown in sterile conditions and original explant is sterilised.

Question 22

Describe the process of micropropagation by callus tissue culture.

Answer 22

1. Take a small sample of tissue from plant — often meristem tissue from shoot tips and axial buds — in sterile conditions to avoid contamination.
2. The explant is sterilised.
3. Place in sterile culture medium containing a balance of plant hormones (auxins and cytokines).
4. Cells proliferate by mitosis forming a mass of identical cells/clumps transferred to a new medium which stimulates growth of plantlets.
5. These are potted into compost to become small plants which are planted out to grow and produce a crop.

Question 23

Give 9 examples of plants that are commonly produced by micropropagation.

Answer 23

1. Potatoes
2. Sugar cane
3. Bananas
4. Cassavas
5. Strawberries
6. Grapes
7. Chrysanthemums
8. Douglas firs
9. Orchids

Question 24

Describe the arguments for micropropagation.

Answer 24

• Can grow plants that are naturally infertile/rare/endangered.
• Geneticaly modified or seedless for consumer’s tastes.
• Known genetic profile.
• Uniform crop
• Disease free
• Any season as tissue culture carried out indoors.

Question 25

Describe the arguments against micropropagation.

Answer 25

• Conditions must be kept sterile — aseptic conditions and any infected cultures must be disposed of.
• Expensive
• If source material ins infected with virus, clones will be too.
• Large number of plants can be lost in the process.
• Produces monoculture
• Labour intensive
• Explants and plantlets are vulnerable to infection by moulds/other diseases during production.

Question 26

Describe 5 examples of natural cloning in animals.

Answer 26

1. Mitotic parthenogenesis — development of an embryo from an unfertilised egg formed by mitosis rather than meiosis so has full number of chromosomes.
2. Damage — animal damaged — multiple pieces develop into new organism.
3. Monozygotic twinning — one zygote splits and forms 2 embryos.
4. Budding — New organism develops from an outgrowth or bud due to cell division at a particular cite. Attached until mature.
5. Fragmentation — organism split into fragments which each develop into mature, fully grown individuals.

Question 27

Explain how, in some species, offspring may be procured without a mate but are not clones.

Answer 27

• Parthenogenesis in which an egg is ‘fertilised’ by another egg or similar gamete, both from the mother.
• Due to the different alleles and random assortment and crossing over of meiosis which created the eg, the offspring, although genetically similar, will not be clones.

Question 28

Define ‘monozygotic’ and describe how identical twins occur.

Answer 28

• Monozygotic twins are formed from a single fertilised egg.
• It occurs when one egg is fertilise by one sperm and one zygote forms. At some point, the early embryo splits into two and each half grows into a new individual.

Question 29

State the two ways of artificially cloning animals.

Answer 29

1. Embryo splitting
2. Somatic Cell Nuclear Transfer (SCNT)

Question 30

Describe the process of cloning animals by splitting embryos.

Answer 30

1. Gametes fuse to form zygote.
2. Embryo develops to the 16-cell stage.
3. Embryo is separated to individual cells.
4. Each cell now develops further into a separate and identical embryo.
5. Surrogate mothers have uterus made ready by hormonal treatments: increased vascularisation, and uterus wall thickness prepares for pregnancy.
6. Each embryo is implemented into a surrogate mother.
7. Surrogate mothers carry cloned embryos to term.
8. Identical cloned offspring born.

Question 31

Define the process of cloning animals by nuclear transfer.

Answer 31

1. A donor cell is taken from the adult organism to be cloned (either male/female, and allows productions of another organism of a species using all possible genetic material and without needing a breeding female of the species).
2. Egg donor is super ovulated with hormones to procure many eggs, harvested from the ovaries. This may be from a closely related species to that providing the nuclear material.
3. The nucleus from the donor cell is removed and the cytoplasm discarded.
4. The nucleus is removed from the donor egg — enucleated.
5. Donor nucleus and enucleated oocyte are fused by the application of an electric current causing membranes to fuse.
6. The fused cell begins to divide normally, forming an embryo.
7. Surrogate mother has uterus made ready by hormonal treatments.
8. Embryo is placed in the uterus of surrogate mother. This may be an animal of a closely related species.
9. Embryo develops normally in the surrogate mother’s uterus.
10. Cloned organism is born with identical nuclear genetically material to the donor animal but with different mitochondrial DNA from the organism that provided the oocyte.

Question 32

Describe arguments for animal cloning.

Answer 32

• Artificial twinning enables high yielding farm animals to produce many more offspring than normal reproduction.
• Guarantees success of passing on desired characteristics.
• If used to prevent rare animals from going extinct, it will prevent loss of genes/alleles from the species.
• Infertile animals can be reproduced.
• SCNT allows scientists to clone specific animals e.g. pets/top race horses.
• SCNT allows GM embryos to be replicated and develop, giving many embryos from one engineering procedure.
• SCNT has the potential to enable rare/endangered/extinct animals to be reproduced.

Question 33

Describe cons for animal cloning.

Answer 33

• Animals become genetically uniform, increasing susceptibility to disease.
• Animals may have low quality of life/shortened life span.
• Many cloned embryos fail to develop and miscarry, or produce malformed offspring.
• Not just desirable characteristics are passed on to their offspring.
• Difficult, time-consuming, and expensive.
• SCNT has been relatively unsuccessful so far in helping endangered or extinct animals.
• SCNT is very inefficient — in most animals, it takes too many eggs to produce a single cloned offspring.
• Work force must be highly trained which is expensive.