Selective Breeding, Genetic Modification and Cloning Flashcards
How can selective breeding be used to develop plants or animals with desired characteristics?
- Select the plants or animals with desired characteristics beneficial to humans
- Breed these plants or animals together
- Choose the offspring with desired characteristics and breed these together
- Repeat over many generations
Unlike natural selection, the characteristics of these animals will not necessarily grant them the best chance of survival
What desired characteristics may be sought after in plants or animals?
- Disease resistance
- Higher crop/meat/milk yield
- Appearance/taste
- Resistance to certain conditions
What are problems with selective breeding?
- Inbreeding, causing a reduction in the gene pool and a lack of varierty which can lead to harmful genetic defects and vulnerability to the same disease
- Ethical concerns
How do restriction enzymes and ligase work to cut out a gene from an organism and insert it into a plasmid?
- The gene to be inserted is located in the original organism
- A restriction enzyme is used to cut out a gene from a section of DNA, leaving sticky ends (a short section of DNA with unpaired bases)
- The same restriction enzyme is used to cut out a section of DNA in a plasmid, leaving it with corresponding sticky ends to the original organism
- The gene from the original organism is joined to the sticky ends in the plasmid by ligase enzymes
- If the sticky ends are corresponding, an unbroken section of DNA will be formed in the plasmid and it will become a recombinant plasmid
- Recombinant means containing genes from two or more organisms
- This is the method to insert a new gene into a plasmid so that this plasmid can be inserted into a bacterial or yeast cell, so here the plasmid is acting as a vector
How do vectors work to insert a recombinant gene into a cell?
- Plasmids act as vectors for bacteria and yeast, while viruses act as vectors for humans cells and bacteria
- They will be genetically modified (as outlined previously) and then inserted into a cell
- This genetically engineered cell will then divide and retain the modified plasma
How can insulin be produced by genetically modified bacteria?
- The human insulin producing gene is cut out of a human cell and added to a plasmid (in the method earlier described)
- This engineered plasmid is inserted into a bacterial cell
- This bacterial cell will multiply, making many bacterial cells all producing insulin
- This bacteria can then be placed inside a fermenter where the conditions are controlled to mass produce insulin
Bacteria are useful as they contain the same genetic code as us, raise no ethical concerns and have plasmids which are easy to modify
How can genetically modified plants be used to improve food production?
- Plants can have DNA inserted into them from other organisms
- This can provide them with favourable characteristics
- They be modified to: Produce a poison that renders them resistant to pests, become resistant to herbicides so only weeds are killed when sprayed, grow faster and with more food, contain more nutrients, be drought or disease resistant
- Most of these things will improve crop yield as well as the quality of the food
GM crops are transgenic, so will have their genes coming from another organism such as a bacterium to give them their traits
What are the disadvantages of genetically modified crops?
- Risk of the inserted gene being transferred to nearby plants, meaning weeds will become herbicide/disease resistant and can spread
- The use of herbicides to kill all other plants can reduce biodiversity
- The resistance to pests can reduce biodiversity of bees etc.
- The seeds and fruit is more expensive, and many people are conceptually challenged by GM crops
How does the process of micropropagation produce clones of a plant?
- Cells known as explants are scraped from the plant you want to clone
- They are sterilised, and transferred to a petri dish containing nutrients
- They will each grow into a small mass of cells known as a callus, and then each callus is added to a larger volume of nutrient medium with growth hormones to encourage the growth of roots, a stem and leaves
- The new plantlets formed are then transferred to soil, giving you a cloned plant
- You must always keep the plants until optimal conditions, such as keeping the environment sterile ot prevent bacterial competion
- This is like taking cuttings, however on a larger and more scientific scale
What are the advantages and disadvantages of micropropagation?
- A plant with very desirable characteristics can be quickly cloned with a gurantee the new plants will possess its characteristics
- If you have genetically modified it, this only needs to have been done once
- The desired plant will result in a greater yield, better food, etc. and grow faster
- However it is very expensive and trained personnel and laboratories are required
- The organisms are also all genetically identical so will not adapt to changing conditions and will be vulnerable to disease
Micropropagation can be used commerically to mass produce plants with desired characteristics
What is the process of cloning animals?
- A nucleus from a body cell of the organism you wish to clone is extracted
- An unfertilised egg cell is extracted from a female of that organism and the nucleus is removed
- The nucleus from the original organism’s body cell is then inserted into the enucleated egg cell, and a small electric shock stimulates the egg cell to begin dividing to form an embyro
- It is then inserted into the womb of a surrogate mother, which could be any female of that organism
- The resultant organism is genetically identical to the first organism, and possesses no DNA from any other source
This has been done in real life as illustrated by Dolly the Sheep in 1996
What are the advantages and disadvantages of cloning animals
- Agricultural animals with desired characteristics can be produced rapidly with a guarantee they will possess the same genes, so genetic modification does not need to be repeated
- Yield and quality of animals is therefore increased
- Rare species can be preserved
- However the new population is less adaptable and are vulnerable to disease
- There are many ethical concerns especially as this could lead to the cloning of humans
How can animals be used for producing human proteins?
- Similar to bacteria producing insulin, an animal such as a sheep is genetically modified, making it into a transgenic organism
- This organism now possesses a gene or genes which allow it to produce a specific protein useful to humans, and can be cloned to produce many of this animal
- An example is GM sheep that produce milk containing human antibodies for fighting cancer
