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  • Created by: Elena
  • Created on: 10-04-13 13:29

Bacterial Cells

  • Bacterial cells have a cell wall to help them keep their shape and stop them from bursting
  • They have a strand of DNA in the cytoplasm that controls the cell's activities and replication. Som also have several loops of DNA called plasmids
  • They sometimes have a flagellum (tail) to help them move
  • They come in 4 shapes: rods, curved rods, spheres and spirals
  • Bacteria can consume a huge range of organicn nutrients from their surroundings. This proides them with energy.
  • This means that different bacteria can survive in almost any habitat e.g. soil, water, air etc
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Bacteria - Asexual Reproduction

  • Bacteria reproduce by asexual reproduction - they're clones of each other. They reproduce by binary fission
  • Bacteria reproduce very quickly
  • Bacteria reproduce faster when it's warm and there's a good source of nutrients. This is why it's important to store food carefully.
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Aseptic Technique - Culturing Bacteria

  • You can culture bacteria on an agar plate. Bacteria can be transferred to the plate from a sample using a wire inoculation loop.
  • When you culture bacteria, it's important to use aseptic technique to protect yourself from infection and to stop the agar from  being contaminated by other microbes. This involves:
  • Wearing gloves and keeping long hair tied back
  • Sterilising equipment before and after use e.g. passing the inoculation loop through a Bunsen burner flame to kill any unwanted bacteria onto it
  • Disposing of cultures safely after use - usually done by pressure sterilising in an autoclave
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Bacteria Can Be Used To Make Yoghurt

  • The equipment is sterilised to kill of any unwanted microorganisms
  • Then the milk is pasteurised - again to kill of any unwanted microorganisms. Then the milk's cooled
  • A starter culture of Lactobacillus bacteria is added. The mixture is incubated (heated to about 40 degrees) in a fermenter. The bacteria break down the lactose sugar in the milk into lactic acid. The lactic acid causes the milk to clot andd solidify into yoghurt
  • A sample is taken to make sure it's at the right consistency. Then flavours and colours are sometimes added and the yoghurt is packaged.

P.s Why do we even need to know this?

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Viruses Reproduce Inside Living Cells

  • Viruses aren't cells. They're usually no more than a protein coat aronud a strand of genetic material
  • They can only reproduce inside living cells, so they must infect other organisms in order to multiply
  • Viruses can infect plant, animal and bacterial cells
  • A particular type of virus will only attack specific cells

How a virus reproduces:

  • The virus attaches itself to a specific host cell and injects its genetic material into the cell
  • The virus then uses the host cell to make the components of new viruses
  • This eventually causes the host cell to split open - releasing the new viruses
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Disease Transmission

  • In food - you can get ill from eating food that's been contaminated with bacteria. It can be prevented by good hygiene and by making sure food is cooked properly before consumption
  • In water - You can get infected with cholera by drinking water that's been contaminated with sewage. Good sanitation can prevent cholera and other waterborne diseases
  • By airborne droplets - flu and other viruses can be spread via tiny airborne droplets released when you cough or sneeze.
  • Through contact - the fungus which causes athelete's foot can be spread by people walking in bare feet on damp floors.
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Poor Sanitation

  • The incidence of a disease is the number of new cases that occurs in a population in a certain time
  • Good sanitation and public health measures are linked to a low incidence of disease. A clean water supply, good sewage works, public health education and clean hospitals prevent the spread of disease
  • Poor sanitation is linked with a high incidence of disease.
  • Developing countries are less likely to be able to afford good sanitation and public health measures
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Infectious Diseases

  • Firstly, the microorganism enters the body e.g. through the nose/mouth
  • One the microorganism is in the body, it reproduces rapidly, producing many more microorganisms
  • The microorganisms then produce toxins which damage cells and tissues
  • The toxins cause symptoms of infection e.g. pain/stomach cramps. Your immune system's reaction to the infectino can also cause symptoms e.g. fever. The time between exposure to the microorganism and the development of the sympoms is called the incubation period.
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Antiseptics and Antibiotics

  • Antiseptics and anitbiotics are chemicals that destroy bacteria or stop them growing
  • Antiseptics are used outside the body to help clean wounds and surfaces. They're used to prevent infection rather than treat it. Plenty of household products contain antiseptics. Antiseptics are also used in hospitals and surgeries to try to prevent infections like MRSA
  • Antiobiotics are drugs used inside the body, usually taken as a pill or injected. They're used to treat people who are already infected. They only kill bacteria though - viruses aren't affected by antibiotics
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Antibiotic Resistant Bacteria

  • Random mutations in bacterial DNA can lead to changes in the bacteria's characteristics. Sometimes, they mean that the bacteria are less affected by a particular antibiotic
  • Bacteria with these genes are better able to survive and reproduce in a host who's being treated to get rid of the infection
  • This leads to the gene for antibiotic resistance being passed on to lots of offspring. The gene spreads and becomes more common in a population of bacteria over a period of time
  • Bacteria that are resistant to antibiotics (e.g. MRSA) are very hard to treat
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Finishing Antibiotics

The more antibiotics are used, the bigger the problem of antibiotic-resistance becomes. It's more important that doctors only prescribe antibiotics when it's really necessary

It's not the antibiotics that actually cause the resistance, but they do create a situation where naturally resistant bacteria have an advantage and so increase in numbers. If they won't do you any good, it's pointless to take antibiotics

It's important that you take all the antibiotics a doctor prescribes for you; lots of people stop bothering taking their antibiotics when they feel  better, however this increases the risk of antibiotic resistant bacteria emerging, so you must complete the course of drugs.

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Diseases and Natural Disasters

Natural disasters like earthquakes and hurricanes can damage the infrastructure of an area, and completely disrupt health services. In these conditions disease can spread rapidly among the population

  • Some natural disasters damade sewage systems and water supplies. This can result in contaminated drinking water containg the microorganisms that cause diseases like cholera
  • People can become displaced when their homes are destroyed. They might move into temporary camps with large numbers of other people and poor sanitation. In these conditions, diseases can spread easily
  • Health services can be disrupted by damaged transport links, allowing infections to spread rapidly
  • Electricity supplies are also often damaged by natural disasters. This mean that food goes off quickly as fridges can't work - this can lead to an increase in food poisoning
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Louis Pasteur

Until the 19th century people didn't understand how diseases were caused/spread. People used to think that diseases spontaneously appeared from nowehere. Louis Pasteur argued that there are microbes in the air which cause disease and decomposition. Pasteur carried out experiments to prove this theory:

  • He heated broth in two flasks, both os which were left open to the air. However, one of the flasks have a curved neck so that bacteria in the air would settle in the loop, and not get through to the broth
  • The broth in the flask with the curved neck stayed fresh, proving that is was the microbes and not the air causing it to go oss
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Joseph Lister

When Lister first started working as a surgeon, hospital conditions were unhygienic. Nearly half of patients undergoing surgery died from infections of their wounds, known as sepsis

Lister's observations of wounds led him to think sepsis was a type of decomposition. He knew about Pasteur's work on microbes in the air. He realised he needed to kill microbes that were getting into wounds from the air

Lister began to treat and dress wounds using the antiseptic carbolic acid. This killed the bacteria in the wounds and prevented sepsis. Gradually, Lister's techniques were taken up by the rest of the medical profession.

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Alexander Fleming

Fleming was clearing out some plates containg bacteria. He noticed that one of the plates of bacteria also has mould on it and the area around the mould was free of the bacteria

He found that the mould (Penicillium notatum) on the plate was producing a substance that killed the bacteria - this substance was penicillin.

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Yeast Respiration

When yeast respires anaerobically it produces ethanol, carbon dioxide and energy. This is fermentation: glucose --> ethanol + carbon dioxide (+ energy)

Yeast can also respire aerobically. This releases more energy than anaerobic respiration. Aerobic respiration is the same for yeast as it is for plants and animals:

glucose + oxygen --> carbon dioxide + water (+ energy)

Whether the yeast repire aerobically or anaerobically depends on whether there's oxygen present. Yeast prefer to respire aerobically (as it releases more energy), so fermentation only takes place in the absence of oxygen

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Yeast's Growth Rate

The faster yeast respires, the faster it's able to reproduce. The speed that yeast respires/reproduces varies. It's growth rate is controlled by the temperature, availability of food, pH and how quickly waste products can be removed:

  • Yeast reproduces faster when it's warmer. But if it gets too hot the yeast dies
  • The more food there is, the faster the yeast reproduces
  • Build-up of toxic waste products slows the rate of reproduction
  • The pH has to be just right. Too high or low pH slows down reproduction

Yeast also reproduces faster in the presence of oxygen. This is because it's able to respire aerobically, giving it more energy for reproduction

One way of measuring how fast the yeast's reproducing is to measure how much glucose it breaks down. The faster yeast produces, the more glucose will be broken down

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Wastewater Can be Cleaned Up with Yeast

Food-processing factories need to get rid of sugary water. They can't just release it into waterways as it would cause pollution. Bacteria in the water would feed on the sugar and reproduce quickly, using up all the oxygen in the water. Other organisms in the water that need that oxygen (like fish) die

Yeast can be used to treat the contaminated water before it's released - it uses up the sugar in respiration

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Brewing with Yeast

Beer -

  • Beer is made from grain - usually barley
  • The barley grains are allowed to germinate for a few days, during which the starch in the grains is broken down into sugar by enzymes. Then the grains are dried in a kiln. This process is called malting
  • The malted grain is mashed up and water is added to produce a sugary solution with lots of bits in it. This is then seived to remove the bits.
  • Hops are added to the mixture to give the beer its bitter flavour

Wine -

  • The grapes are mashed and water is added

Yeast is added and the mixture is incubated. The yeast ferments the sugar into alcohol. The fermenting vessels are designed to stop unwanted microorganisms and air getting in. The rising concentration of alcohol in the fermentation mixture due to anaerobic respiration eventually starts to kill the yeast. As the yeast dies, fermentation slows down. Different species of yeast can tolerate different levels of alcohol.

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Brewing with Yeast (Continued...)

The beer and wine produced is drawn off through a tap. Sometimes chemicals called clarifying agents are added to remove particles and make it clearer.

The beer is the pasteurised. Wine isn't pasteurised - any yeast left in the wine carry on slowly fermenting the sugar. This improves the taste of the wine. Beer also tastes better unpasteurised and aged in the right conditions. But big breweries pasteurise it because there's a risk unpasteurised beer will spoil if not stored in the right conditions after it's sold.

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Distillation Increases the Alcohol Concentration

  • Sometimes the products of fermentation are distilled to increase the alcohol content. This produces spirits e.g. if can sugar is fermented then distilled, you get rum
  • Distillation is used to seperate the alcohol out of the alcohol-water solution that's produced by fermentation
  • The fermentation products are heated to 78 degrees, the temperature at which alcohol boils and turns into vapour
  • The alcohol vapour rises and travels through a cooled tube which causes it to condense back into liquid alcohol and run down the tube into a collecting vessel
  • The distillation of alcohol is a commercial process that can only be done on licensed premises.
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Biomass and Biogas

Biomass is living or recently-dead organic material. It's also a store of energy. The energy stored in biomass can be transferred into more useful forms e.g.:

  • fast growing trees can be burnt, releasing heat
  • biomass can be fermented by yeast and bacteria to create products such as biogas, which can be used as fuel


  • Biogas is usually made of about 70% methane and 30% carbon dioxide. It also contains trace amounts of hydrogen, nitogen and hydrogen sulfide
  • Biogas containing more than about 50% of methane burns easily, but if it contains around 10% methne is can be explosive
  • Biogas is made by bacteria in a digester. The bacteria's respiration produces methane
  • Biogas can be used as fuel
  • Biogas can be burned to power a turbine, which can be used to generate electricity. This is especially useful for producing electricity in remote areas with no mains supply
  • Biogas can be burned to heat water and produce steam to heat central heating systems
  • It can also be used as fuel for cars and buses
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Biogas is Made by Anaerobic Respiration

  • Biogas can be made from plant waste and animal faeces in a simple fermenter - a digester
  • Several different types of bacteria are used to produce biogas. Some decompose the organic matter and produce waste, then another type decompose that waste, and so on, until you get biogas. This process is a type of fermentation
  • Biogas digesters need to be kept at a constant warm temperature (30-40 degrees). This is the optimum temperature for the bacteria's respiration. It also needs to be anaerobic
  • A simple biogas generator needs to have:
  • an inlet for waste material to be put in
  • an outlet for the digested material to be removed through
  • an outlet so that the biogas can be piped to where it's needed
  • Large scale biogas production uses a continuous flow method - organic waste is continuously fed into the digester, and the biogas and solid digested material are continuously being removed at a steady rate
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Biofuels - Advantages

  • Biofuels can be produced in a sustainable way. The crops which are decomposed to make biogas can be replaced quickly with new plants. In contrast, there's a finite supply of fossil fuels like coal and crude oil
  • The plants grown to make biogas photosynthesis. This removes carbon dioxide from the atmosphere and can balance ou the release of carbon dioxide from burning the biogas. This is only true if:
  • the biofuels are burnt at the same rate that the new biomass is produced
  • areas of land are cleared to grow biomass without burning other vegetation. When the vegetation is burnt it releases more carbon dioxide into the atmosphere
  • Biogas is a cleaner fuel than diesel or petrol. Burning these fossil fuels produces particulates which can cause lung disease. Burning biogas doesn't produce particulates
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Biofuels - Disadvantages

  • Biogas doesn't contain as much energy as the same volume of natural gas because it's more dilute
  • Large areas of land are sometimes are cleared of vegetation to create space to produce biofuels. As well as increasing greenhouse gas levels, this can create huge problems for ecosystems:
  • habitat loss - as plants are cleared, the habitats of many plant and animal species are destroyed
  • extinction of species - the loss of habitats and a change in food availability might mean the some species die out in the area
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Biofuels - Ethanol

  • Ethanol can be burnt as fuel. It's a cleaner fuel than petrol or diesel, producing fewer pollutants
  • Ethanol is a renewable resource. It is produced by using yeast to ferment glucose. Materials like sugar cane, corn and barley can be used as a source of glucose for this
  • Cars can be adapted to run on a mixture of ethanol and petrol - gasohol. Gasohol is a mixture of about 10% ethanol and 90% petrol
  • Using gasohol instead of pure petrol means that less crude oil is being used up (petrol is refined from crude oil, which is non-renewable)
  • Another advantage is that the growth of crops for ethanol productions emans that carbon dioxide is being absorbed from the atmosphere in photosynthesis. This goes some way towards balancing out the release of carbon dioxide when the gasohol is burnt
  • Some countries, such as Brazil, have made extensive use of gasohol. It's most economically viable in areas where there is plenty of sugar cane and not a lot of oil
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Different Soils Contain Different Particles (fasci

  • Sandy soils are made up of large mineral particles. Becaues the particles are so large, they leave large pores in the soil - this means that sandy soils often have a high air content and are very permeable
  • Clay soils are mostly made up of tiny particles. The small partiles can pack tightly together and leave very small pores in the soil - so clay soils usually have a low air content and low permeability. They tend to retain more water than sandy soils because the water molecules cling to the small particles
  • Loam soils contain a mixture of sand and clay particles. Their properties depend on the relative amounts of the different types of particles
  • Most soils also contain humus - decomposed, dead organic matter. Humus helps support soil life
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Structure of Soil - Experiments

Measuring the water and humus content:

  • take the mass of a small sample of soil
  • heat the sample to 105 degrees until it reaches a constant mass - this will boil off all the water in the soil
  • take the mass of the soil sample again - the different between the first and second reading is the mass of water in the original soil sample
  • heat the soil sample to 550 degrees for two hours - this will burn all the humus
  • take the mass of the soil again. The difference between the second and third reading is equal to the mass of humus in the original soil sample

Measuring the air content:

  • loosely pack a sample of soil into a beakerand measure the volume of soil
  • fill up a pipette with a known volume of water and gradually add it to the beaker, letting it seep down into the soil. Continue doing this until the water comes to the top of the soil
  • as the water has replaced the air in the soil, the volume of water added is the same as the volume of air in the original soil sample
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Life in the Soil

  • Plants need soil for anchorage and for a supply of minerals and water. Animals needs plants for food and oxygen
  • Soil is an ecosystem containing complex food webs. Herbivores, carnivores and detritivores are all found in the soil
  • There are several other types of organism that live in the soil - microscopic protozoans, fungi, nematode worms and bacteria
  • In order for soil to support life, it must contain water and oxygen. All living things need water to carry out reactions in their cells and can't survive without it. Almost everything needs oxygen too, for respiration
  • The presence of humus also helps support life:
  • as organic material is slowly broken down by decomposers, minerals and nutrients are released into the soil. These compounds can then be used by other organisms.
  • humus also increases the air content of the soil, making more oxygen available to the organisms that live there
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Earthworms are good for soil structure and fertility:

  • earthworms bury leaves and other organic material in the soil, where bacteria and fungi can decompose them
  • their burrows allow air to enter the soil (aeration) and water to drain through it. Aeration provides the soil organisms with oxygen, but drainage is also important. If the soil is waterlogged, there'e less oxygen available
  • they mix up the soil layers, distributing the nutrients more equally
  • soil in earthworms faeces is less acidic than the soil they eat. This can help to neutralise soil acidity. Acidic soils are less fertile than neutral or alkaline soils
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Living in Water - Advantages and Disadvantages

  • Advantages -
  • There's a plentiful supply of water
  • In water, there's less variation in temperature.
  • Water provides support for plants/animals that have no skeletal system.
  • Waste disposal is easier. The loss of water in urine doesn't matter beacuse there's plenty of water about to make up for it
  • Disadvantages -
  • Water is more resistant to movement than air, so animals living in water have to use more energy to move about
  • Aquatic animals have to be able to control the amount of water in their body, this is because the water an animal lives in has a different concentration of solutes form the animal's cells:
  • if the animal lived in salt water its cells would probably contain a lower solute concentration than the surrounding water. If tha animal wasn't able to regulate water then water molecules would leave its cells by osmosis, causing them to shrivel and die
  • if the animal lived in fresh water its cells would probably contain a higher solute concentration than the surrounding water. If the animal wasn't able to regulate water, then water molecules would enter its cell by osmosis, causing them to swell and burst
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Amoebas and Plankton

Most single-celled oraganisms, like amoebas, only have a cell membrane between them and the surrounding water. So they regulate water like this:

Amoebas regulate water with a contractile vacuole which collects the water that diffuses in by osmosis. The vacuole then moves to the cell membrane and contracts to empty the water outside the cell.  

Plankton are microscopic organisms that live in fresh and salt water. There are two types:

  • Phytoplankton are microscopic plants
  • Zooplankton are microscopic animals. Zooplankton feed on phytoplankton

Phytoplankton photosynthesise and are the main producers in aquatic food webs so they're very important in both freshwater and salt-water ecosystems

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Plankton Populations

Photosynthesis is affected by temperature, light intesnsity and the availablity of minerals like nitrates. These factors vary at different depths and different seasons:

  • duing the winter months and in deep water, light intensity and temperature are low. Mineral concentration on the other hand, is relatively high. In these conditions, light intensity and temperature limit the rate of photosynthesis
  • during the summer months and in shallow water, light intensity and temperature are higher but mineral concentration is much lower. This limits the amound of photosynthesis

Phytoplankton populations usually increase between late spring and late summer - an algal bloom. The increase is due to longer, sunnier days:

  • more light is available for photosynthesis and the energy is used for growth
  • temperatures increase, causing both photosynthesis and growth rates to increase
  • the population of zooplankton also increases because there's more phytoplankton to feed on
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Food Webs in the Oceans

  • Most ocean food webs are 'grazing food webs' - they begin with a living producer.
  • Producers in ocean food webs are often phytoplankton. But in deep water where light can't penetrate, photosynthesis can't take place. So some grazing food webs are supported by bacterial producers that rely on sulfur from deep sea vents
  • In other deep-sea food webs, animals often feed on dead, decomposing material that has slowly fallen from nearer the surface. This 'marine snow' is the major source of nutrients for these food webs
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Causes of Water Pollution - Fertilisers and Sewage

Fertilisers and sewage - causes eutrophication:

  • fertilisers and sewage enter water, adding extra nutrients
  • algae grow rapidly
  • algae die and decay
  • bacteria feed on dead algae, using up oxygen in the water
  • animals are unable to respire and die

Some organisms are particularly sensitive to the level of oxygen in the water. These species are used by scientists to indicate how polluted the water is (the less oxygen, the more polluted). For this reason, they're called indicator species.

Species that are sensitive to different pHs can also be used as indicator species. By seeing which species lives in a particular area, scientists can made a pretty good estimate of the pH

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Causes of Water Pollution - Industrial Chemicals a

Chemical which have caused water pollution include pesticides and industrial chemicals. If water is polluted by these, they are taken up by organisms at the bottom of the food chain. They aren't broken down by the organisms, so when they're eaten the chemical is passed on. The concentration of the chemical increases as it is transferred up the food chain because each organisms eats many of the organisms below it.

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Biological Washing Powder

  • Some stains are caused by soluble chemicals and so they wash out easily in water. Stubborn stains contain insoluble chemicals like starch, proteins and fats.
  • Non-biological washing powders (detergents) contain chemicals that break up stains
  • Biological washing powders contain the same chemicals as non-biological ones, but also contain a mixture of enzymes which break down the stubborn stains
  • Biological washing powders usually work best at moderate wash temperatures because the enzymes are denatured by high temperatures. However, some newer powders contain enzymes that are more resistant ot heat and so can be used with a hotter temperature
  • Biological washing powders might not work very well in acidic or alkaline tap water. This is because the enzymes can be denatured by extremes of pH
  • You can buy special stain remover. Some of these are just special solvents, but some certain specific enzymes that will break down the stain
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Medical Products - Enzymes

  • Diabetes is diagnosed by the presence of sugar in urine.
  • Reagent *****s (*****s of paper with enzymes and chemicals in them) are used, they're dipped in the urine and change colour if sugar is present
  • The test is based on a sequence of enzymes reactions. The product of the enzyme controlled reactions causes a chemical embedded in the ***** to change colour
  • There are similar *****s which can be used to test blood sugar levels
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Food Industry - Enzymes

Low calorie food:   

  • table sugar is what you normally sweeten food with at home
  • in the food industry sucrose (or invertase) is used to break down sucrose into glucose and fructose. Glucose and fructose are much sweeter than sucrose
  • this means you can get the same level of sweetness using less sugar. This helps to make low-calorie food sweeter without adding calories


  • the enzyme rennet is used to clot milk in the first stages of cheese production

Juice extraction: 

  • the enzyme pectinase is used in fruit juice extraction. It breaks down pectin (a part of the cell wall in apples and oranges), causing the cell to release its juice
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Immobilising Enzymes - Removal

  • Many industrial processes use immobilised enzymes, which don't need to be seperated out from the mixture after the reaction has taken place
  • Enzymes can be immobilisedin different ways. One way to incapsulate them in alginate beads (alginate is a gel-like substance). The beads are formed by mixing the enzyme with alginate, then dropping the mixture in to a calcium chloride solution
  • The immobilised enzymes are still active and help speed up reactions

Advantages -

  • the enzymes don't contaminate the product
  • immobilised enzymes in alginate beads can be used in continuous flow processing
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Immobililsed Enzymes - Used to Mke Lactose-Free Mi

  • The sugar lactose is naturally found in milk. It's broken down in your digestive system by the enzyme lactase. This produces glucose and galactose, which are then aborbed into the blood
  • Some poeple lack the enzyme lactase. If they drink milk the lactase isn't broken down and gut bacteria ferment it, causing abdominal pain, wind and diarrhoea - lactose intolerance
  • Lactose-free milk can be produced using immobilised lactase. The lactase breaks down lactose into glucose and galactose. These simply sugars can be aborbed by someone who's lactose intolerant.
  • Continuous flow processing is often used for this:
  • the substrate solution (milk) is run through a column of immobilised lactase
  • the enzymes convert the substrate (lactose) into the products (glucose and galactose), but only the products emerge from the column. The enzymes stay fixed in the column
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Immobilised Enzymes - Used in Reagent Strips

  • Diabetics use reagent *****s to measure their blood glucose concentration on a daily basis. They're quick and convenient to use.
  • There are immobilised enzymes on the reagent *****s
  • A drop of blood is added to the *****. The enzymes in the ***** cause it to change different colours depending on the glucose concentration. The colour is then compared to a chart to find out the level of blood sugar
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Transferring Genes Between Different Organisms

  • Genetic engineering alters the genetic code of an organism. A gene giving a desirable characteristic is removed from one organism and inserted into another organism
  • We;re able to transfer genes from one organism to another because the genetic code is universal
  • A genetically modified organism is called a transgenic organism
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Genetic Engineering

  • Identify the gene that you're after in an organism
  • Remove the gene from the organism's Dna
  • Cut open the DNA of the organism that you want to put the gene into
  • Insert the gene in to the DNA of the second organism - where the gene should now work
  • The host is now a transgenic organism. You can clone it to produce more copies

The cutting and inserting of DNA is done using enzymes

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Bacteria Can be Engineered to Produce Human Insuli

  • Scientists identify the gene which controls the production of human insulin
  • They remove it from the DNA of a human body cell by 'cutting it out' with restriction enzymes. This leaves the DNA with 'sticky ends'
  • A loop of bacterial DNA called a plasmid is then prepared for the insulin gene to be inserted. Restriction enzymes are used to cut open the plasmid, leaving it with sticky ends too
  • The insulin gene is inserted in the plasmid. The sticky ends allow another enzyme callsed ligase to join DNA strangs together. This plasmid is then taken by bacteria (the plasmid is known as a vector - something that carries a gene in to another organism)
  • The bacteria are now transgenic organisms. They're checked to make sure they contain the new gene using assaying techniques and are then cultured by cloning. Millions of bacteria can be produced in this way, allowing large quantities of insulin to be harvested
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DNA Fingerprinting

  • You DNA is unique (unless you're an identical twin)
  • DNA fingerprinting is a way of comparing DNA samples to see if they come from the same person or from two different people
  • DNA fingerprinting is used in forensic science. DNA taken from a crime scene is compared with a DNA sample from a suspect
  • It can also be used in paternity tests
  • Some people would like everyone's genetic fingerprints to be stored on a national genetic database. That way, DNA from a crime scene could be checked against everyone in the country to see whose it was. But others think this is a big invasion of privacy, and they worry how safe the data would be and what else it might be used for. There are also scientific problems - false positives can occur if errors are made in the procedure or if the data is misinterpreted
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Fingerprinting - How It Works

  • First, you have to extract the DNA from the cells in your sample
  • Restriction enzymes are then used to cut the DNA in to fragments. They cut it at every place where they recognise a particular order of bases. Where these sections are in the DNA will be different for everyone
  • If the DNA sample contains that little section of bases lots of times, it'll  be cut into lots of little bits and vice versa
  • The DNA bits are seperated out using electrophoresis. The fragments are suspended in a gel, and an electric current is passed through the gel. DNA is negatively charged, so it moves towards the positive anode. Small bits travel faster than bit bits, so they get further through the gel
  • The DNA is 'tagged' with a radioactive probe. Then it's palced into photographic film. The film goes dark where the radioactivity is, revealing the positions of the DNA fragments.
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Miss Meera J


haha. p.s Why do...

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