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Biology A level - Cloning and Biotechnology Cheat Sheet by

This is based on the OCR A Gateway spec for A level biology, Chapter 22 from module 6. Specification reference: 6.2.1

Natural cloning in plants

Bulbs e.g. daffodils
Leaf bases contain stored food, buds develop internally and make new shoots.
Lateral stem grows, eventually withers away.
Rhizomes e.g. marram grass
Specia­lised horizontal growth, stem develops buds -which becomes new plant.
Stem tubers e.g. potatoes
Tip of underg­round stem becomes swollen with stored nutrients. Buds develop on that storage organisms and form new shoots.
Uses in hortic­ulture:
Can take cuttings from bulbs/­runners to increase the yield because it is faster than growing seeds.
This also guarantees quality (because geneti­cally identi­cal).
e.g. used in sugar cane cloning.

Artificial cloning in plants

Sample taken from meristem (sterile condit­ions).
Steril­ised. Collected tissue = explant.
Placed in sterile culture medium containing plant hormones. Cells form Mass of identical cells (callus).
Callus is divided and transf­erred to different medium. This stimulates the develo­pment of geneti­cally identical plantlets.
Plantlets are planted in compost and grow.
Young plants planted out to grow as crops.

Artificial twinning and SCNT

Artificial twinning
Animal w/ desired trait is given hormones for super-­ovu­lation.
Ova is fertilised in vitro or by insemi­nation (by desired male).
Before 6 days, cells are split (still totipo­tent).
Each cell becomes an embryo.
Embryos are inserted in surrog­ates.
Develop into foetuses and born normally.
Somatic Cell Nuclear Transfer (SCNT)
Transfer nucleus from adult somatic cell into enucleated egg cell (no nucleus).
Nucleus and egg are fused with an electric shock
OR electr­ofusion - Cells are left next to each other with constant current running through.
+ More offsprings than usual
+ Guarantees desirable genes from sire.
+ Useful in pharming
+ Can clone rare and endangered animals
- SCNT = ineffi­cient -- many eggs required to succes­sfully produce one offspring.
- Cloned embryos fail to develop, produced deformed offspr­ings...
- Most clones have a shorter lifespan, which also means we have not been successful in cloning extinct species yet.

Biotec­hnology and microo­rga­nisms

Applying biological organisms / enzymes to the synthesis / breakdown / transfer of materials in the service of people
e.g. foods, penici­llin, insulin...
Pros / cons of using microo­rga­nisms:
+ No ethics
+ Easily manipu­lated geneti­cally
+ Short life cycles
+ Simple + cheap nutrient requir­ements
+ Growth conditions = low temper­atures / oxygen / food...
- Can produce toxins
- Have to be separated from nutrient and processed.
- Sterile conditions needed (increases cost).
- Less natural flavour.

Direct / indirect food production

Indirect food prod
Use microo­rga­nisms for their effects on other foods.
e.g. bread -- yeast caused it to rise.
yoghurt -- bacteria make it sour.
Direct food prod
Grow microo­rga­nisms to eat
e.g. Quorn, fusarium venetatum (grown on glucose syrup).


Indirect food production
Yeast anaero­bically respires.
Optimum temp about 20-28oC, but can also be geneti­cally modified to function at lower temper­atures.
Malting - Barley germinates and digests starch into sugars so yeast respires.
Mashing - Malt + hot water. Enzymes break down starch, worth is formed.
Fermen­tation - Wort + yeast. pH a lowered as yeast runs out of O2 and produces ethanol.
Maturation - Low temper­atures for about a month.
Finishing - Filtered, pasteu­rised and bottled with CO2.

Baking bread

Indirect food prod
Yeast feeds on sugars and ferments them into ethanol and CO2 which makes the bread rise
Optimum temp. of 38-46oC
Optimum pH - 5.0 / 5.5
Yeast requires O2 and sugars for fermen­tation.


Indirect food prod
Bacteria feed on lactose, inhibit growth of bacteria which makes milk go off.
Pasteu­rised - 95oC for 20 seconds.
Mixed with bacteria culture and enzymes. The milk is separated into solid curds and liquid whey.
Cheese - Curds are separated and cooked in whey, sometimes pressed and dried.


Indirect food prod
Skimmed milk powder, milk is pasteu­rised and cooked.
L. bulgarius / S. thermo­pilus bacteria added to the milk and milk is stored at cool temepr­atures.

Cultiv­ating microo­rga­nisms

Inocul­ating broth
Bacteria suspen­sion, mixed with sterile nutrient broth. Incubated and shook.
Inocul­ating agar
Inocul­ating loop Sterile and dipped in suspen­sion. Streaks made across a Petri dish.

Biorea­ctors - making penicillin

Semi-c­ont­inuous batch
Fungus grows and produces penici­llin. The drug is extracted and purified.
The container is sealed to avoid contam­ination (asepsis).
The mixture is constantly stirred so it stays oxygen­ated.


Microo­rga­nisms are used to break down pollutants and contam­inants in soil / water.
Natural organisms
Used on crude oil / sewage.
GM microo­rga­nisms
Break down material they don't normally encounter (e.g. mercury in water).

Bacterial growth stages

Lag phase
Bacteria adapting to environment.
Growing and synthe­sising enzymes.
Expona­ntial phase
Close to / at theore­tical max.
Stationary phase
Growth rate = zero --> Cells formed cancelled out by cells dying.
Death phase
Reprod­uction almost stopped, death rate increases (resources used up).

Bacterial growth graph

Serial dilutions

Immobi­lised enzymes

Altern­ative to using microo­rga­nisms is to isolated their enzymes.
Immobi­lised enzymes are when those enzymes are fixed so substrate washes over them.
+ Reusable so cheaper, greater temper­ature tolerance, less downstream proces­ssing.
Surface immobi­lis­ation - Surface adsorption (sticking to the surface) to inorganic carrier.
+ Simple and cheap.
+ Activity virtually unchanged.
- Enzymes can be lost from matrix easily.
Surface immobi­lis­ation - covalent / ionic binding to inorganic carrier.
+ Enzymes bound strongly, unlikely lost.
+ Accessible to substrate.
+ pH / substrate concen­tration = little effect on activity.
- Cost varies
- Active site may be modified.
Entrapment - in matrix.
+ Applicable to different processes.
- Expensive.
- Difficult to entrap.
- Diffusion can be slow.
Entrapment - encaps­ulation or semi-p­erm­eable membrane.
+ Relatively simple to do.
+ Small effect on enzymes activity.
+ Applicable to different processes.
- Expensive.
- Diffusion can be slow.


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