Cloning

Question 1

Define cloning

Answer 1

Process of creating cells or organisms that are genetically identical to the parent organism from the cells of the parent.

Question 2

Give the 4 types of cloning

Answer 2

• Asexual reproduction.
• Artificial cloning by nuclear transfer.
• Artificial cloning by tissue culture.
• Artificial vegetative propagation.

Question 3

Advantages of asexual reproduction

Answer 3

• Quick, allowing organisms to reproduce rapidly and take competitive advantage over resources in habitat.
• Can be carried out if sexual reproduction not possible/fails (no second parent).
• Offspring genetically identical to parent, so will possess all characteristics that allow parent to be well adapted to environment.

Question 4

Disadvantages of asexual reproduction

Answer 4

• Does not produce genetic variation, so all offspring susceptible to and will be affected by same weaknesses. E.g. A new disease or an unsuitable change in climate could wipe out whole offspring population.
• Offsprings are generally in vicinity of parent, so there will be competition.

Question 5

Define vegetative propagation

Answer 5

Production of structures from non-reproductive tissue of parent plant that develop into completely new individuals, often genetically identical to parent, so are considered clones.

Question 6

How does vegetative propagation occur in elm trees

Answer 6

1. Suckers grow from sucker buds scattered across root that are normally dormant,
2. Sucker buds activated and suckers begin to grow from shallow roots when elm tree experiences stress (e.g. Disease, damage) or is dying.
3. Suckers are usually well spaced out from parent to avoid factor/s causing stress on parents but all grow in a circle around parent called clonal patch.
4. They eventually grow into completely new elm trees that are clones of the parent.

Question 7

How are plants cloned artificially

Answer 7

• Stem cuttings.
• Leaf cuttings.
• Root cuttings.
• Grafting.
• Tissue cultures

Question 8

How are stem cuttings carried out

Answer 8

• Part of a plant stem is cut from parent plant.
• The stem section is replanted in soil and treated with plant hormones to encourage root growth.
• Stem grows into full plant and is clone of parent.

Question 9

How are grafting carried out

Answer 9

• Grafting can only be used for cloning woody plants.
• A shoot section (scion) of one plant is joined to the rootstock of another plant and is held in place.
• The scion grows into new plant and eventually fuses with rootstock.

Question 10

How are tissue cultures carried out

Answer 10

1. Tissue sample (called explant) containing many meristematic cells are taken (usually shoot tip).
2. Cells are sterilised to kill potential contaminants.
3. Cells are placed on nutrient growth medium and allowed to divide into unspecialised mass called callus.
4. Single callus cells are then taken and placed into growth medium containing shoot stimulating hormones.
5. Shoots are then transferred to medium containing root stimulating hormones.
6. Developing plantlets are then transferred into compost and left to grow in greenhouse (or other protected environments).

Question 11

What are the advantages of tissue cultures over traditional plant cloning techniques

Answer 11

• Some plants to not reproduce well from cuttings/ graftings.
• Large number of cloned offsprings can be produced quicker compared to traditional techniques.
• Minimal damage to parent plant as only small tissue sample needed as opposed to say, a whole stem.
• Cloned plants can be produced at any time of the year as tissue cultures are carried out indoors.

Question 12

What are the advantages of plant cloning

Answer 12

• Parent’s desirable characteristics are always passed to offspring, due to having same genetic information.
• Cloned plants can be produced at any time of the year as tissue cultures are carried out indoors.
• Sterile plants are allowed to reproduce.
• Quick as some plants take long time to grow from seeds.
• Clones grow at same rate so are ready to harvest around same time, reducing farmers’ costs

Question 13

What are the disadvantages of cloning plants

Answer 13

-

Question 14

What are the methods for cloning animals?

Answer 14

• Embryo splitting.

- Nuclear transfer.

Question 15

How is embryo splitting carried out?

Answer 15

1. Early developing embryo (8-16 cells) taken from womb of mother and put into cell culture.
2. Embryo carefully split into multiple embryos and are transferred to womb of genetically unrelated surrogate mothers.
3. Embryos develops in womb of surrogates to produce identical offsprings.

Question 16

How is nuclear transfer carried out (in sheep)?

Answer 16

1. Somatic (body) cell from sheep A taken and nucleus extracted.
2. Egg cell from sheep B is enucleated.
3. Sheep A nucleus inserted into the enucleated sheep B egg cell.
4. Egg cell stimulated to divide into embryo in vitro.
5. Developing embryo then implanted into another sheep, acting as surrogate mother.
6. Lamb produced is genetically identical to sheep A so is clone.

Question 17

What are the advantages of cloning animals?

Answer 17

• Parent’s desirable characteristics are always passed to offsprings due to having same genetic information.
• Infertile animals can reproduce and pass on good traits.
• Large number of offsprings can be produced very quickly.
• Can be used to clone rare species and preserve population when suitable mates are difficult to find.

Question 18

What are the disadvantages of cloning animals?

Answer 18

• Parent’s undesirable characteristics are always passed to offsprings, so they are vulnerable to same weaknesses.
• Technically very complex and requires many failed attempts to produce success, which may be costly and time consuming.
• Cloned offsprings may not live as long as natural offspings.

Question 19

What is reproductive cloning?

Answer 19

Creation of whole genetically identical organism (clone) using cells from the parent

Question 20

What are the uses of reproductive cloning

Answer 20

• Used for testing drugs and other research. Individuals are genetically identical, eliminating any variations caused by genetic differences, making results more reliable.
• Used in agriculture to replicate individuals with desirable characteristics.
• Used to clone endangered species and increase population size in endangered species if mates are difficult to find/ sexual reproduction slow.

Question 21

What is non-reproductive cloning

Answer 21

Use of cells in parent to produce embryonic stem cells with identical genetic information to parent. This is also called therapeutic cloning.

Question 22

What are the uses of non-reproductive cloning

Answer 22

• Produces embryonic stem cells of a (developed) individual.
• These are totipotent, so can differentiate into any type of tissue cell.
• They can be used to grow replacement tissue for those damage due to disease/ accident. E.g. Replace nervous tissue lost to MS, replace cardiac tissue lost after heart attack etc.
• Can be used to potentially grow replacement organs.
• These stem cells are genetically identical to parent cells, so won’t be classed as foreign by immune system, so no rejection suffered.

Question 23

What are the ethical issues concerned with human cloning

Answer 23

• Use of embryos as source of stem cells destroys embryo, which had the potential of developing into human being.
• Cloned humans, if produced, may have reduced quality of lived as consequence of social acceptance and identity.
• Cloning may undermine the traditional ‘family’.