Cloning

Front 1

What are clones

Back 1

By definiton, a clone is an exact copy, but in biology it describes genes, cells or whole organisms that carry identical genetic material because they are derived from the same original DNA

Front 2

How are clones produced in eukaryotes and how are they produced in prokaryotes

Back 2

In eukaryotes - clones are generated through mitosis whereas in prokaryotes - cloning occurs through division by binary fission.

Front 3

What are the advantages of asexual reproduction

Back 3

- It is quick, allowing organisms to reproduce rapidly and so take advantage of resources in the environment
- It can also be completed if sexual reproduction fails or is not possible
- All offspring have the genetic information to enable them to survive in their environment

Front 4

What are the disadvantages of asexual Reproduction

Back 4

- Doesn't lead to any genetic varity, so any genetic parental weakness will be in all the offspring.
- If the environment changes, for example with the introduction of a new disease causing organism, then all genetically identical organisms will be equally susceptible.

Front 5

What is vegetative propagation i.e. in the Elm trees

Back 5

Vegatative propagation is the way in which plants naturally reproduce asexually e.g. the English Elm when damage occurs to parent plants
- This allows them to survive catastrophies e.g. disease or burning via root suckers
- They sprout up in a ring around the tree known as the clonal patch

Front 6

What is the advantage of elm tree vegatative propagartion

Back 6

- It allows the elm to spread because they can grow all around the original trunk when the tree is stressed or trunk dies.
- the suckers grow into a circle of new elms called the clonal patch
- However, because the clones are genetically identical they are prone to the same diseases, e.g. when Dutch Elm disease came to England - the elm trees grew root suckers, however, the new trees got infected and died too.

Front 7

Describe the principle of taking cuttings

Back 7

- Taking cuttings - section of stem is cut between leaf joints and the cut ends are often treated with hormones to encourage root growth and planted. The cuttings form a new plant which is a clone

Front 8

Describe the principle of grafting

Back 8

A shoot section of a woody plan is joint to an already growing root and stem and the graft grows and is genetically identical to the parent plant, but the rootstock is genetically different.

Front 9

Describe the production of artificial clones of plants from tissue culture (also known as micro-propagation)

Back 9

Used because cuttings and grafts cannot produce large numbers of clones

1) A small piece of tissue is taken from the plant to be cloned, usually from the shoot tip called the explant (meristematic tissue)
2) The explant is placed on a nutrient growth medium and sterilised
3) the cells in the tissue divide, but they do not differentiate. Instead they form a mass of undifferentiated cells called a callus
4) After a few weeks, single callus cells are removed from the mass and placed on a growing medium containing plant hormones to encourage shoot growth
5) After a further few weeks, the growing shoots are transferred onto a different growing medium containing different hormone concentrations that encourage root growth e.g. cytokinins and auxins
6) The growing plants are transferred to a greenhouse and then planted outside into sterile soil.

Front 10

What are the advantages of plant cloning in agriculture

Back 10

- Desirable genetic characteristics e.g. high fruit production are passed on to clones. This doesn't always happen when plants reproduce sexually
- Plants can be reproduced in any season because tissue cultures are carried indoors
- Sterile plants can be reproduced
- Plants that take long time to produce seeds can be reproduced quickly

Front 11

What are the disadvantages of plant cloning in agriculture

Back 11

- Undesirable genetic charactersitics e.g. producing fruit with lots of seeds are always passed on to clones
- Cloned plant population have no genetic variability, so a single disease can wipe them all out
- Production costs are very high due to high energy usage and training of skilled workers

Front 12

What are the two methods of artificially cloning animals

Back 12

- Splitting embryos - cells from a developing embryo can be separated out, with each one then go on to produce a separate, genetically identical organism
- Nuclear Transfer - using enucleated eggs

Front 13

Describe Splitting embryo technique in detail

Back 13

1) Select two individuals with certain desired characteristics and collect eggs and sperm from each one.
2) Fertilise the eggs in vitro and grow to small embryo
3) Split the embryo into several separate segments
4) Implant into surrogate mothers

Front 14

Describe nuclear transfer

Back 14

1) Remove mammary cells from udder and extract the nucleus and keep it.
2) An egg cell is removed from another sheep, with its nucleus also removed to form an enucleated egg cell
3) The nucleus from sheep A is inserted into the enucleated egg cell so the Sheep B has the same genetic information as sheep A (by electrofusion
4) The egg cell is stimulated to divide until an embryo is formed.
5) In reproductive cloning - the embryo is implanted into a surrogate mother and a lamb is produced that's genetically identical to A
6) In non-reproductive cloning, stem cells are harvested from the embryo which are genetically identical to cells from sheep A.

Front 15

What are the advantages of cloning animals

Back 15

- High value animals e.g. cows giving high milk yield, can be cloned in large numbers
- Rare animals can be cloned to preserve the species
- Genetically modified animals - for example sheep that produce pharmaceutical chemicals in their milk - can be quickly reproduced

Front 16

What are disadvantages of animal cloning

Back 16

- High-value animals are not necessarily produced with animal welfare in mind e.g. some strains of meat producing chickens have been developed that are unable to walk
- As with plants - excessive genetic uniformity in species could make them unable to adapt to and change to environment
- Unclear whether cloning animals will allow them to remain healthy in the long run e.g. premature ageing

Front 17

What is reproductive cloning

Back 17

- Reproductive cloning is used to make a complete organism that's genetically identical to another.
- Scientists can use cloned animals for research purposes, e.g. testing new drugs as clones have same genetics making the tests more reliable
- Farmers can use it to increase the number of animals with desired characteristics to breed.

Front 18

What is non-reproductive cloning

Back 18

- Non reproductive cloning is used to make embryonic stem cells that are genetically identical to another organism (also called theapeutic cloning)
- Embryonic stem cells are harvested