Explain using an appropriate example from agriculture why selective breeding has been practiced
Selective breeding improves quality and yield of production from farm animals and crops. It involves crossing varieties to:
Combine favorable characteristics and allow better productivity, called hybrid vigour.
Can produce better nutritional value
Gain resistance to disease
Show tolerance to drought and cold
For example, Hereford cattle selectively bred with Brahman cattle to produce Brahfords that have heat and tick resistance and good growth rates and foraging skills.

Analyse and present information from secondary sources to trace the history of the selective breeding of one species for agricultural purposes and use available evidence to describe the series of changes thathave occurred in the species as a result of this selective breeding
Wheat - 1788 wheat farmed in Australia but can only be grown in areas with abundant rainfall and favourable soil
Australia’s poor soil and uncertain rainfall – insufficient crop yield diseases such as stem rust would further destroy the crops

Wheat - 1889
Farrer began a wheat breeding program using varieties from all over the world characteristics he sought to breed were rust resistance, early ripening and good bread-making properties(high gluten levels) wheat strains from India gave best early ripening characteristics and also had short stems and more grainsper wheat stalk
Farrer released his ‘Federation Wheat’ in 1902 which matured early and escaped rust - damage and had high yield soon, most wheat grown in Australia was Federation Wheat and it was able to withstand dry climate andharsh heat of
Australia

Fine wool merinos
Over the past 300 years, farmers have selectively bred fine wool merinos. In doing so, they selected merino rams with favourable characteristics to sire offspring that will inherit these favourable characteristics. The aim of selectively breeding merinos is to produce tougher animals that produce wool of a higher quality and quantity.
Over the past 300 years: fibre strength increased fibre diameter and length decreased coat density increased animal hardiness increased

Describe what is meant by ‘gene cloning’ and give examples of the uses of gene cloning
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Gene cloning: The process of selecting a particular gene, cutting it out of the
DNA and inserting it into anotherorganism where copies are made.
A gene is cut out of the chromosome using restriction enzymes. ‘Sticky ends’ are formed where cuts are made.
Circular DNA (plasmid) from a bacteria and cut using the same restriction enzyme3
The gene is mixed with the bacteria plasmid and DNA ligase is used as a ‘glue’ to allow the gene and plasmid to recombine at matching sticky ends4
Plasmids are reinserted back into bacteria by adding calcium chloride to increase permeability of bacteria membrane
Bacteria reproduces and plasmids are cloned, cloning the recombinant genes
The bacteria will also express the protein now introduced into its genome

Applications of recombinant genes production of human insulin to treat diabetics
(e.g. putting gene for insulin into E.coli) production of human growth hormone to treat stunted growth production of proteins that dissolve blood clots to treat heart attacks and other heart problems production of bacteria that can break down toxic wastes from oil spills

Describe the processes used in the cloning of an animal and analyse the methodology to identify ways inwhich scientists could verify that the animal produced was a clone
The process by which animals are cloned is called Somatic Cell
Nuclear Transfer (SCNT)
Nucleus from a body cell (somatic cell) of an organism to be cloned is taken and starved of nutrients soit does not divide.
An egg cell is taken from another animal of the same species and the nucleus is removed.
The somatic cell is inserted into the egg cell and an electrical stimulus is used to fuse them and stimulate cell division.
At a certain stage in cell division, the embryo is implanted into a female surrogate mother.

Techniques to identify a clone:
DNA hybridisation can be used to tell whether two organisms are genetically identical with strands of each organisms DNA separated by heat and then one strand from each put together. Single strands matching up indicated a clone.
Fingerprinting and profiling looking at bands can be used to match DNA of two organisms
The original and the clone organism can be determined using mitochondrial and chloroplast DNA which will not be the same in each organism, despite cloning.

Discuss a use of cloning in animals or plants that has possible benefits to humans
Uses:
Cloning plants for agriculture using tissue cultures
Tissue cultures are a way of cloning plants where a tissue sample (from the meristematic tissue) is taken and grown in a suitable environment such as soil or an agar plate.

Benefits include:
Preserving biodiversity for future generations by cloning endangered species
Cloning newly discovered or genetically engineered species to better propagate and spread superiorcrops, e.g. BT cotton
Increasing natural resources, e.g. cloning trees for furniture
Genetically identical plants will produce a uniform product which is more desirable for consumers, e.g.same colour on oranges
Less costly and time consuming then continually selective breeding

Disadvantages lie in the fact that genetic diversity is decreased.
If there is a selective pressure such as a diseaseor pest there may be no plants with resistance and so the whole population could be easily wiped out.