5.12 Restriction and Ligase enzymes

Describe the use of restriction enzymes to cut DNA at specific sites and ligase enzymes to join pieces of DNA together

1. Restriction enzymes 

• are enzymes that cut DNA molecules at specific points
• different restriction enzymes cut DNA at different places
• they can be used to cut specific genes from a molecule of DNA 

2. DNA ligases 

• are enzymes that join cut ends of DNA molecule
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

OBJ - 5.11 Breeding animals

 Understand that animals with desired characteristics can be developed by selective breeding.

1. Farmers breed animals for similar reasons to the breeding of crops. They have selected for animals that:

• produce more meat, milk or eggs
• produce more fur or better quality of fur 
• produce more offspring
• show increases resistance to disease and parasites 

2. Eg: Cows --> milk/meat

The farmer selects his breeding cows which are producing a high yield ---> they become the breeding population --> they are selected for the desired characteristic. 

As we progressively 'select' we change the desired characteristic by selective breeding. This is done under the control of genes. 

5.10 Breeding plants

Understand that plants with desired characteristics can be developed by selective breeding

Selective breeding 


1. 

• decide which characteristics are important/desired
• choose parents that show these characteristics
• select the best offspring from parents to breed the next generation
• repeat the process continuously. 

2. Crop plants are bred to produce strains that:

• give higher yields 
• are resistant to certain diseases
• are resistant to insect pest damage
• are hardier (so that they survive harsher climates or are productive for longer periods of the year)
• have a better balance of nutrients in the crop 

OBJ 5.9 Fish Farming

Explain the methods which are used to farm large numbers of fish to provide a source of protein, including maintenance of water quality, control of intraspecific and interspecific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding.

1. Attractive features of fish:

• low fat
• high protein 
• efficient at turning their nutrient into fish mass 

2. Fish farming advantages:

• we can control quality of water (clean) 
• we can control predators 
• can reduce pests 
• can reduce bacteria/disease

3. By controlling all these factors, we can contribute to an increase in yield of fish.

4. But where there is there high density of fish --> you get a transmission of disease

5. This leads to farmers using Antibiotics ( a concern to human health) and the high density of fish also means that pests become common ---> farmers use Pesticides --> concern to human health. 

OBJ 5.8 Industrial Fermenter

Interpet and label a diagram of an industrial fermenter + explain suitable conditions 

Aseptic precautions:
- a pipe filled with steam is fed into the fermenter in between sessions to sterilize the fermenter


Nutrients:
- at the start of the process, nutrients are fed in through pipes which can be opened or closed using valves.

Optimum Temperature and PH: (there is a sensitive prob for each)
- Fermentation produces heat, so to prevent the contents from overheating , the fermenter is surrounded by a water jacket in which water circulates, keeping the temperature at the best level for growth. 

- The PH of the contents can be adjusted by adding acid or alkali to keep it constant. 

Oxygenation and Agitation: 
- In the center of the fermenter there are stirring paddels which mix the contents - this keeps the microorganisms in suspension in the liquid so that they get more exposed to the nutrients that are fed in. And the agitation helps keep the temp even throughout the fermenter.

OBJ 5.5 Beer Production

Understand the role of yeast in beer production 

Beer is an alcoholic drink made by fermentation reaction that uses yeast to convert sugars to ethanol.
Fermentation also means "anaerobic respiration." 

1. Sugar from plant material (barley) is converted into ethanol and carbon dioxide by fermentation. Yeast is used as a natural catalyst.

Sugar --> ethanol + carbon dioxide

C6H1206 ---> (enzymes in yeast) --> 2CH5OH +2CO2

2. The starch in barley is first broken down into sugar so that the yeast cells can ferment it to ethanol.

3. When barley seeds germinate (process is called "malting", they produce the enzyme amylase which breaks down starch into maltose - this is used by the yeast as an energy source in fermentation.

4. Sugars for beer-making come from boiling the barley in water - Hops are then added to adjust the flavor of beer making it bitter, and stop bacteria growing. 

The yeast is then added and after a while it uses up all the oxygen in the mixture and startes to respire the sugars anaerobically.

5. Flow of stages in beer production

Barley seeds are germinated - they make amylase to digest starch
-->
Seeds are killed and dreid to make malt
--> 

Malt is ground up and mixed with water in a mash turn - amylase breaks down starch into maltose
-->
Mash is boiled and filtered
-->
Hops are added for taste and yeast is added to ferment sugars making beer
-->

Beer is centrifuged + filtered
-->
Beer is put into casks or barrels

5.4b Biological control

Understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants

1. Pest numbers can be reduced by using using another organism, rather than a toxic chemical.

2. Method examples:

a) introducing a natural predator - ladybirds control population of aphids in orange groves.

b) introducing a herbivore - moth controls the prickly pear (weed) in grazing lands of Australia.

Advantages 

• no toxic chemical
• less impact on wildlife + man

Disadvantages

• not 100% efficient
• difficult to control - danger 
• difficult to match a predator to a prey.