A2 Biology: Cloning

Cloning

• Genes cellsor whole organisms carrying identical genetic material
• Occurs naturally in
• identical twins
• plans which reproduce asexually
• bacteria replicating though binary fission

Asexual reproduction

• Prokaryotes divide by binary fission
• the DNA replicated and the cell divides
• Two cells are genetically identical 
• The basis of asexual reproductions in nearly all eukaryotes is mitosis
• the genetic material replicated to separated to form two nuclei
• the nuclei contains exact copies of the original DNA
• the cells splits to produce two daughter cells that are cloned offspring
• Advantages
• quick - reproduces rapidly - take advantage of the environment
• alternative if sexual reproduction fails or is not possible
• all offspring have the genetic information to enable them to survive
• Disadvantage
• it does not produce genetic variation
• therefore if the environment changes or a new disease is introduce then they are all equally susceptible.

Artificial vegetative propagation 

• taking cuttings
• section of a stem is cut between the leaf joints
• end treated with plant hormones
• plnted = forms ne plants
• grafting
• shoots section is joined to an already growing root and stem
• the graft grows and is genetically identical to the parent plant, but rootstock is genetically different
• advantages
• plants with useful features are identified for growth
• some have to be grown this way - bananas have to be cloned because cultivaed bananas are sterile
• farmers know what features the plant will have - yield, taste, disease resistance etc
• cost reduced because all the crop can be harvested at the same time
• faster
• disadvantages
• plants equally susceptible to new pests or disease
• crops are grown in specific areas and are divided by a certain distance to limit this effect

CLONING ANIMALS

• a cloned animal is one that has been produced using the same genetic information as another animal
• such an animal has the same genotype as the donor organism
• nuclear transfer - dolly the sheep

• splitting embryos
• an embryo can be genetically manipulated
• IVF using the sperm and egg of high value ales and females
• +ve
• high value animals produce in large numbers
• rare animals cloned and preserved
• genetically modified animals can be quickly reproduced
• -ve
• high value animals not produced with animal welfare in mind
• genetic uniformity reduced ability to cope with changes in the environment
• it is unknown how the process effect the long term health of the animals

Non-reproductive cloning

• this is the use of cloned cells to regenerate cells, tissue and organs to replace those that become damages
• +ve
• no rejection by the immune syste
• cloning and cell culture could end the wait for transplantation
• cloned cells are totipotent - generate any cell type (some diseses cannot be treated by transplant)
• likely to be less dangerous
• possibilities include:
• regeneration of heart tissues after a heart attack
• repair or nervous tissues destroyed by diseases such as multiple scleorosis
• repairing the spinal cord
•