Biology B1 - B5

Biology Notes
B1 NOTES: You and Your Genes
Chromosomes: They are found inside the nucleus of cells. They are X Shaped Objects that Contain DNA. Each Chromosome is made from two Chromatids. Chromosomes are held together by a disc called a centromere. Chromosomes are always found in Pairs. | | A | T | G | C | C | G |
DNA: It Stands for Deoxyribonucleic acid. DNA is Made from Nucleic acids of ten (referred to as bases). The four bases are Adenine (A) which always pairs with Thymine (T) and Cytosine (C) which always pairs with Guanine (G). | | T | C | A | G | T | G |
RIGHT WRONG

Genes: A gene is the short length of the chromosome which is a molecule of a DNA. Genes can exist in Different Versions. Different Versions of the same gene are known as ALLELES. Each gene codes for a specific Protein. Some proteins are Structural, meaning they can form skin, hair, blood and cytoplasm. Others are Functional (enzymes) controlling chemical reactions such as respiration or digestion. Genetic Information is stored by Genes who are arranged on Chromosomes.
Variation: This is the Difference between humans. There are two types of variation. The First is Genetic Variation (Caused by your Genes and can’t be changed e.g. your natural hair colour, eye colour). The Second is Environmental Variation (Caused by your surrounding and can be changed e.g. Dying your Hair, Ear Piercings). Genetic Variation: Caused by the DNA in the cells in your body. We Can’t Change this.
Environmental Variation: Caused by your Surroundings, Family and Friends. We can Change this.
Determining Your Gender: A Sperm Cell has an X chromosome and a Y chromosome. An Egg Cell has two X Chromosomes. If the fertilised egg has a X Chromosome from the sperm the Foetus will be a Girl if it has a Y Chromosome (the Chromosome carrying Testosterone) the Foetus will Be a Boy. There is a 50:50 Chance of Having a Boy or a Girl.
Further Gender Determination
Chromosome pair 23 is known as the Sex Chromosomes. There are two Different types of of Chromosome 23 – The X and Y chromosome. The only Difference is that the Y chromosome carries the gene for testosterone, X does not. All Cells carry at least one X Chromosome. Sperm Cells carry either a Y or X chromosome.
Allele – A different version of the same gene.
Heterozygous – When There are two types of an allele in the genotype e.g. Bb – Brown.
Homozygous – When there is only one type of Allele in the genotype e.g. BB(-Brown) or bb(-Blonde).
B = Dominant – Always Expressed, b = Recessive – only expressed in a Homozygous genotype.
Natural Cloning * The Hydra (Plant) Shows Budding * Asexual Reproduction - The Spider Plant and Strawberries often reproduce this way.
Twins: They are formed by the fertilised egg splitting in half and the two halves turn into to two identical babies.
Artificial Cloning
For many years, mammals have been cloned by splitting embryos – Artificial Cloning. There are two types of Artificial Cloning
Cloning Way 1 1. They take an egg cell from one mammal. 2. A Body Cell is taken from a second mammal (the same mammal as the first) 3. The egg cell nucleus is removed from the cell 4. The body cell nucleus is also removed 5. The Nucleus from the body cell is inserted into the egg cell to make a clone of the Second Mammal. 6. The egg cell divides and is put into the uterus of the first Mammal. The Clone grows into a mature mammal.
Cloning Way 2
It isn’t just Reproductive Cloning (Cloning People/mammals) we could use this technology for. Cloning human cells may be useful in treating humans.
Reproductive Cloning – When a baby is born from cloning
Stem Cells
A stem cell is an undifferentiated cell which means they can turn into any type of cell required. They can therefore be used to make organs. They Can be used to replace damaged cells.
Inherited diseases
Cystic Fibrosis * 1 in 200 Children are affected by Cystic Fibrosis. * Is an Inherited disease * They produce thick sticky mucus. This can block the air passages and the tubes that carry digestive juices to the gut. * The Child has trouble breathing and absorbing food. * Patients are treated by chest physio-therapy. * The Mucus is a good breeding ground for germs. * Sufferers often get infections and have to be treated with strong antibiotics. At the moment there is no cure. * Cystic fibrosis is caused by a recessive Allele(c) – So to contract the disease a person must have two recessive alleles (cc). * Heterozygous people (Cc) do not get the disease but can act as carriers and pass it on to their children. * The disease is shown from Birth. * It affects the lungs and gut.
Huntington’s Disease * This is a rare inherited disease. * It affects about 1 in 20,000 * It shows up when the patient is about 30 – 40 years old. * The cells of the brain degenerate and the patient makes clumsy and jerky movements. * The sufferers become moody and depressed. * The memory is affected and they eventually become totally disabled. * Huntington’s disease is caused by a dominant gene – so only one allele is needed to give the disease. * So all heterozygous people are sufferers because the onset of the disease occurs so late many people have produced a family before they find out they have the condition. * The Organ Effected is the Brain.
B2 NOTES: Keeping Healthy
Bacteria cell Bacteria are known as micro-organisms. Many of these cause disease. Those that cause disease are called Pathogens. Other micro-organisms include Protozoans, Fungi and Viruses. Micro Organisms reproduce quickly in warm, damp places. Once inside a host of Pathogens reproduce and cause Infection.
How Pathogens can enter our Body * Nat Bites/ Being Bitten * Eating * Touch * Sexually Transmitted * Bugs * Dogs/ Animals * Breathing it in * Birds * Injections * Cuts * Natural Openings * Blood Transplants * Organ Transplants
Things that protect our Body from Pathogens * Eyebrows/ Eyelashes * Cilia * Acid * Mucus * Tears * Skin * White Blood Cells * Healing over cuts
Gaining Immunity
Example
1) James is Infected by some bacteria that causes a disease 2) The bacteria reproduce and James gets ill. 3) One of James’ white blood cells detect the bacteria. It makes anti bodies to destroy the bacteria. 4) The white blood cells reproduce. Now there are lots of them making Anti-bodies. 5) The bacteria are all killed. James gets better. 6) Most of the white blood cells that make the antibodies die, but a few of them stay in the blood. 7) James is infected with the same bacteria again. 8) The white blood cells to make the antibody are still in James’ Blood. So this time they are ready to kill the bacteria very quickly. 9) The bacteria are killed before they can make James ill. He is Immune to this disease.
Anti-body = A Chemical made by White blood cells which binds to Antigen.
Antigen = A marker on the surface of a Pathogen that identifies it as foreign.
Pathogen = A micro-organism which causes Disease.
White Blood Cells: * Produce Anti-bodies to neutralise the Microbe * They eat the microbe * They produce anti-toxins to neutralise the poisons produced by microbes.
Producing Anti-bodies 1. A White Blood cell detects a pathogen. 2. A White Blood cell produces Anti-bodies. 3. The anti-bodies bind with Antigens. 4. The Pathogen is engulfed by the White Blood Cell.
Natural Immunity
This is when Anti-bodies are produced by a Person when needed or they are passed on by a mother during Pregnancy.
Artificial Immunity
A Vaccine with dead Microbes is injected – the body is ‘tricked’ into producing anti-bodies ready for the real thing. This is called Passive Immunisation.
We should use the new influenza vaccines every year because influenza reproduces very quickly. Also it has a high mutation rate, which means that it changes so you need to continually be protected by Influenza. Especially if you suffer from other illnesses, because you would be at risk the most. Also the antigens would have changed shape.
Vaccinations Policy
Benefits – Wont spread through a large population is a benefit. Also if a woman has a vaccination then falls pregnant she passes the antibodies onto the child.
A vaccine Policy is a decision made by the government to vaccinate a large amount of people. This usually only works if the majority of people agree to it.
Antibiotics
Immunity/ Immune: When your body has already met a Pathogen once and therefore cannot make you ill again
Antibody: These attach to pathogens and Stick the together.
Vaccine/ Vaccination: An inactive or dead version of a pathogen is introduced into the body.
Antigen: The marker on a Pathogen that a White Blood Cell can recognise.
White Blood cells: a Cell that produces Antibodies.
Antibiotics:
* You take them and they kill the bacteria and it makes you better * You have to take them continually * They take a while to settle in * They kill infections * They are produced by Bacteria and Fungi * Are Drugs that are effective at killing Bacteria and Fungi * Antibiotics do not seriously damage body cells * Antibiotics are derived from micro-organisms * Penicillin comes from bread mould and was the first antibiotic discovered. * However they have limited use and have no effect on viruses.
Antibiotics and Superbugs
Antibiotics are used to kill Bacteria and Fungi in an infection in the body. The chemicals are made from Fungi and Bacteria.
Antibiotics are Drugs that kill Bacteria and Fungi without harming body cells. These drugs do not affect viruses.
A Superbug Bacteria is a Mutation to a Normal Bacteria. It is resistant to normal Antibiotics.
How could we help Reduce Superbugs?
Hospitals
Hospitals can make sure that they treat people with the Superbug properly to stop it from spreading. Keep the Hospital Clean. Inject staff to Stop it Spreading, and to make them Immune.
GP
Inject people more Often and Give out Leaflets.
Drug Companies
Make a more effective drug and make a vaccine.
The Public
Allow people to inject them and make them immune.
Antibiotic Resistance
Stages
1. The cell starts to replicate the DNA 2. The cell has had the DNA Replicate. So therefore the cell has elongated. 3. The Cell has started budding. 4. Binary Fission has taken place and the cell has cloned itself.

A Mutation is a change in the bases that make up DNA. These changes can cause a change in a gene. This can change a Protein and thus affect the Characteristics of an Organism.
Drug Trials
It is important to do strict test on drugs to check that they are safe for use, do what they are supposed to do and to check the side effects. Drugs are tested on human cells that have been developed in a laboratory (The drug is tested on different body cells), then it is tested on animals (to see whether it works as well on whole animals as on the cells) before it is used on human patients(these are tested on volunteers).The three drug trials are Double blind(both doctor and patient do not know the drug is new), Blind trial(only the patient does not know the drug is true but the doctor does), and Open trial(both doctor and patient know the drug is new). A placebo is when a doctor gives a patient something that does not contain Drugs. A Placebo is used in blind trials.
The heart and Heart Disease
A Capillary is 1 cell thick, can only take very low pressure and carries both oxygenate and deoxygenated blood.
A vein has a thin outer wall and is a thin layer of muscle and elastic fibre.
An artery has a thick outer wall and is made up of a thick layer of muscle and elastic fibre.
Causes of a Heart Attack * Arteries are blocked * Cardiac arrest * Lack of Oxygen * Caused/linked to Obesity * Can be caused by Shock * Cells die
Heart attacks are usually caused by atherosclerosis, a build-up of fatty material within the walls of the arteries.
What are the Risk factors?
The things that put you at risk are not being active, Smoking, drinking lots of alcohol and having an unhealthy diet. Also key risk factors include age, gender, genes, ethnic background, diabetes, weight, shape, activity levels, blood pressure, cholesterol and Smoking.
How common is it? Heart disease is the biggest killer in the UK. It affects approximately 300,000 people a year. Heart Attacks are often very painful.
B3 NOTES: Life on Earth
Evolution

Primates:
-Apes, Gorilla, Monkey, Orangutan
Primates:
-Apes, Gorilla, Monkey, Orangutan
Humans
Humans

Evolution
Evolution

Dot of Bacteria Sea Animals Monkeys Dinosaurs Vertebrates Humans

Dot of Bacteria Sea Animals Monkeys Dinosaurs Vertebrates Humans

A Species
A Group of Organisms so similar that they can breed together. Also their Offspring can also breed (are fertile).
We know that horses and Donkeys are not the same Species, because when they breed, their offspring are infertile.
Variation
Variation is the differences between Species or differences between Living Organisms.
Variation can be: * Hair colour * Eye colour * Skin colour * Gender * Shoe size * Piercings * Age * Nose size * Height
One type of evidence for evolution is Fossils, another is DNA.

Ethical Reasons for Evolution: 1. Religion – God Created earth, man and Woman. 2. Big Bang Theory – Meteorite crashed and made the Planets. 3. Life came from outer space – Aliens put humans on Earth. 4. Life started from a single cell – Bacteria Cell evolved into humans.
Darwin’s Discovery
Darwin himself: * Born 1809 * When he was 22 he got the chance to work on a sailing ship – HM Beagle * Out on the Ship for 5 years.
Darwin’s Finches: * 10,00 years ago – moved from South America to the Galapagos Islands * They adapted to the different environment when the Islands Changed
Natural Selection 1. Large beak – Nuts and Seeds 2. Small Pointed beak – bugs and berries
Nerves and Neurons
Your Nervous System sends electrical messages along nerves to and from different parts of your body.
It goes like this: Stimulus then Receptor then Co-ordinator, then Effector and finally Response.
The Co-ordinator is the part of the body that decides what to do.
The CNS is also called the Central Nervous System. The brain and the Spinal Cord are the CNS.
The Senses are touch, sight, smell, hear and taste.
Receptors- are pain sensors in your skin and detect the changes.
Effectors- bring about the responses.
Sensory Neurones – a message from the CNS is send along this.
Motor neurons – Muscles and glands. The CNS sends a message along the motor neuron to these.
A relay Neuron is the third neuron.

Nerves Sense | Sensory Organ | Receptors | SightSmellSoundTasteTouch | EyeNoseEarMouth/TongueSkin(or Hands/Fingers) | LightChemical in the AirVibration(Sound) and BalanceTexture/Pressure/Pain/TemperatureChemicals in Food |

Neurone – A nerve cell that is used to transmit electrical messages through the body. There are three types Sensory, Relay and Motor
Myelin Sheath – A fatty Deposit found on the long axons of neurons. This acts to speed up the process of electrical transmission of messages across the neurone.
Receptor – Are groups of specialised cells. They can detect changes in the environment, called Stimuli, and turns them into electrical impulses. These are often cells found in Sense Organs.
Stimulus – A Change in the environment detected by a receptor that produces a response from the body.
Effector – Part of the body that produces a response. This is normally a muscle, for example, a muscle moving an arm, squeezing a gland or releasing a hormone into the blood.
Reflex Action
Stimulus -> Receptor -> Sensory neurone (-> Synapse) -> Relay Neurone ->Spinal Cord -> Motor Neurone ->Effector -> Response
Hormonal Control
Processes controlled by Hormones * Puberty * Mood Swings * Moustaches * Producing Egg and Sperm
Hormones are chemicals that travel through your body to certain organs.
A Hormone is a chemical that is secreted by a gland and travels in the blood stream to target organs in the body.
Main Glands: * Thyroid Gland * Pancreas * Adrenaline Gland * Testes * Ovaries Nervous | Hormonal | * Faster as the send Electrical Message * Can occur in more places * Only occurs for a certain amount of time * Travel using nerves * Electrical impulses * Quick Acting | * Slower as they travel in bloodstream * Only happens in certain organs/glands * Can occur longer * Travel in Blood * ChemicalsTravel at the speed of blood (slow acting) |

Homeostasis – is the maintenance of the internal environment e.g. body temperature, amount of water in body.
Interdependence Competition and Extinction
Competition: Defined as the simultaneous demand by two or more organisms for limited environmental Sources. E.g. light, Habitats/Space, Food/minerals, Water, Mates, Oxygen/ Carbon Dioxide. In a Food Chain the arrows represent energy transfers between organisms. However, only around 5% of energy is actually passed when an organism is consumed.
Efficiency = Useful Energy (x100 for percentage) Total Energy
Carbon Cycle
How is carbon used by Different Organisms? Plants breathe it in and animals and humans breath it out and use it for excretion. Humans also use it for glucose.
What happens to the carbon once it enters the organism? Plants – Convert it into glucose
Animals – Do what plants do but in reverse
What happens to the carbon once the organism dies? Plants/ Animals – It decomposes, caused by bacteria and CO2 is released.
Combustion – Fossil fuels are being burnt releasing Carbon Dioxide into the air.
Photosynthesis – Sunlight and carbon dioxide help a plant grow and create glucose
Decomposition – when an animal or plant dies it rots and its remains (minerals) are in the soil.
Respiration – CO2 is breathed into the air and to produce sugar for plants.
Detritions – releases CO2 into the atmosphere from decomposed animals and plants.
The Nitrogen Cycle
Nitrogen is found in the air, in the soil and organisms contain nitrogen. Nitrogen is used by plants and animals for energy, making their bodies stronger.
Nitrification – Nitrogen + oxygen is added. Bacteria makes nitrate from ammonia. NH3 -> NO3-
De-nitrification – Oxygen is taken away -> nitrogen makes N2
Nitrogen Fixing – The Nitrogen gives its nutrients to plants and animals.it splits up and has hydrogen added and becomes Ammonia. It is used up but becomes nitrogen again. It occurs in root nodules.
Extinction
Endangered: endangered is when an animal or plant is in danger of becoming extinct.
Extinct: extinct is when a whole species of animals has been run down and killed/ not around anymore. When a species of plants/animals die out.
Extinction can be caused by: * Destruction of Habitat * Lack of food * Over hunting – By people or Animals * Diseases * Changes in environment * Pollution * Pesticides * Competition * Litter * Lack of shelter * New Species * Lack of water * Another species in the food chain becomes extinct * Lack of mating * Human Activity – Indirect –Cutting down trees or use of electricity/Cars/CO2 – ice caps(polar bears) * Human Activity – Direct – Hunting or Shooting
Biodiversity
Biodiversity means the variety of life on Earth. Biodiversity is important because: * It maintains lots of food chains * Keeps ecosystems going * We depend on different species for many things * Many medicines have come from wild plants and animals * For food colouring * A lot of different products come from animals/plants of different species
Sustainability – keeping an area in the state it is without human intervention. It is essentially preserving biodiversity on earth.
B4 NOTES: The Processes of Life
Cells
Plant cells have cell walls to stop the cell from bursting from too much water. Name of Cell Part | What it is/does | Nucleus | Stores DNA | Cytoplasm | Is where most chemical processes take place, controlled by enzymes | Cell Membrane | Let’s/stops things passing through into or out of the cell. | Chloroplast | Absorbs the suns light | Vacuole | Stores waste products and enzymes breaks waste down – keep the cell turgid (swollen). | Cell Wall | Strengthens the cell | Ribosomes | Make proteins in the cell | Mitochondria | The sight of respiration, releases energy within the cell. | Flaccid – Not swollen
Turgid – Swollen
Enzymes
* They are protein molecules which speed up chemical reactions in living things. * They are called Biological Catalysts. * They are found in all living cells * Starch is made up of Glucose * Active Site – gap in Enzymes * Once the substrate is all the way in the active site the enzyme breaks it down and we now have the product.
In the stomach, enzymes and substrates move, if an enzyme and substrate that fit exactly together the enzyme will break down the substrate, and leave you with a product. But the enzymes active sight and the substrate have to be complementary.
When the stomach heats up the reaction rate increases, meaning the amount of products made increases.
Enzymes are made of protein molecules. They are found in the stomach and saliva fluids. They breakdown things like starch and fat. The active sight and substrate fit together like a lock and key to weaken the bonds in the substrate, creating the products. The active sight is a specific shape. Enzymes work slower in low temperature, because the lower the temperature, the lower the ezyme move because they have less energy, which means that there are less collisions with substrates, which means less products. They work faster up to 40 degrees because the gain more energy but if the temperature goes over 40 degrees you end up with denatured enzymes. Denaturation means when the body is higher than 40 degrees the protein bonds in the enzyme breaks up and the shape changes.
Photosynthesis
Dependant Variable – something in an investigation that you measure.
Independent Variable – something in an investigation that you change.
Control Variable – something in an experiment/ investigation that you keep the same.
Carbon Dioxide + Water (+ light Energy) = Glucose + Oxygen
CO2 + H2O (+ Light Energy) = C6H12O6 + 02
6 CO2 + 6 H2O = C6H12O6 + 6 O2
Adaptations for Photosynthesis
Factors that affect Photosynthesis – Light intensity, heat, amount of Carbon Dioxide in the air and amount of water.
Diffusion – Movement of molecules from an area of high concentration. The molecules then become evenly spread.
Stomata are only ever found on the bottom of a leaf. They are pores in the bottom of a leaf that let in and out gases. They will close up at night.
Osmosis
Osmosis – the movement of water from an area of high water concentration to an area of low water concentration across a semi permeable membrane. Isotonic solution is when water moves in both directions. Hypotonic solution is when water moves into the cell. Hypertonic Solution is when water moves out of the cell.
Anaerobic Respiration
Anaerobic Respiration Equation: Glucose = Lactic Acid + Energy
Anaerobic Respiration also happens in: * Plant roots in waterlogged soil * Bacteria in puncture wounds
Investigating in the field
What factors affect plants growth ability in certain areas? * Competition * Shelter * Soil moisture/ Soil type * Weather * Heat * Amount of Light * Amount of Water * Animals around * Deforestation * Soil Composition (Nitrates and pH) * Effect of other Organisms * Light Intensity for Photosynthesis
B5 NOTES: Growth and Development
Cells, Tissues and Organs
Cell – The basic unit which living things are made of.
Tissues – A group of the same types of cells working together.
Organ – A group of tissues that carries out a particular function.
Specialised Cell – A cell that has been adapted to their role. Cell | Tissue | Organ | * Mucus secreting * Enzyme secreting * Bone * Blood | * Epithelial Tissue * Skeletal muscle * Smooth muscle * Cardiac muscle * Nervous tissue * Connective tissue * Adipose tissue * Fibrous connective * Blood * Bone * Loose connective tissue * Cartilage * Crown tissue | * Stomach * Tooth * Skin * Lungs * Ear * Heart | Embryo Development
Conception: Sperm Cell fertilises the egg – this may take up to 24 hours – the fertilised egg cell multiplies, first division after 1 day, then the nucleus splits.
5 Days: divides into 500 cells and divides into two, grows into stem cells.
7 Days: - reaches end of Fallopian tube and reaches the Uterus.
2 Weeks: - starting to take shape and is no bigger than a pin head. The Top of cell becomes the head.
15 Days: - Nerve cells develop, head and Spinal Cord.
3 Weeks: - First organ – heart – before a dormant clump of muscle, triggers different heart cells creating a chain reaction later – brain controls the heartbeat.
4 Weeks: - as big as a kidney bean growing 1mm per day, organs start developing.
8 Weeks: - looks more like a baby (foetus) placenta is now mature.
Earlier – mum and Foetus have different blood vessels.
Now – blood stream connects and placenta stops harmful substances from passing through (except Alcohol and Nicotine)
Placenta – nerve centre of pregnancy. Mothers heart works faster as her body works faster.
10 Weeks – 14 Weeks: First Scan
11 Weeks: Building Blocks for walking, leg reflexes, and more the foetus moves the stronger it will be.
12 Weeks: Sexual organs working, entering second trimester, less at risk of a miscarriage
16 Weeks: - The foetus begins to practise movement, fingers and toes separate, bones harden. * Hands develop before feet * Beginning to develop awareness, sensory organs.
18 Weeks: - Mum becomes aware of baby’s movements (movements strong enough) * Some baby’s open their eyes (blinking reflex)
24 Weeks: - Eyes Open
25 Weeks: - eyelashes are grown and eye colour is not yet formed
26 Weeks: - 25cm Long (head to bottom)
6 Months: Functioning as it will when born all developed but senses.
3rd Trimester: - Sense form- nerves, eyes, ears etc. * First taste and smell of mothers cooking – helps with breastfeeding as it will recognise the taste * Can hear conversations, noise and music * Mothers voice is different and it can hear it more clearly * Reacts if prodded through body * Can feel pain * Reacts to sudden noise – startled reflex * Swallows half a litre of amniotic fluid every day * Perfects the sucking reflex * He will triple in weight and double in length
Stem Cells
Stem Cell – a cell that changes into whatever is need ed in the body. They are unspecialised cells (cells that haven’t been adapted to do a specific job.
Cell Division: Mitosis and Meiosis
Mitosis is used for: * Making new body cells for growth and repair * Asexual Reproduction
Meiosis is used for: Making new Sex Cells and Sexual reproduction
Mitosis
In a normal cell you can’t see the chromosomes. When they start to divide the chromosomes become visible. Each of the daughter cells needs 23 pairs of chromosomes so the chromosomes in the parent cell double up. So when the Cell splits in two, the doubled chromosomes split. This creates two daughter Cells which are identical copies of the parent cell.
Meiosis
Meiosis is the same as Mitosis except the Cell splits again because the daughter cells only need 23 chromosomes as they are Sex Cells (Gametes). After the first split, the chromosomes start to line up again to get ready for the divide and start to split again to create four Daughter Cells, which are different to the parent Cells.
Structure of DNA
DNA Molecules – two strands twisted together into a double helix.
DNA Strands – Smaller molecules including bases.
Bases link the two strands together like the rungs of a ladder. They can be seen more easily if we unwind the DNA molecule.
4 Bases: A (Adenine), C (Cytosine), G (Guarine), AND T (Thymine)
The A, C, G and T bases in the DNA of a gene are joined up in a particular order. The order of the bases is like a code which describes to the cell how to make proteins. This is why DNA is called a genetic code. When replicating DNA the strands and bases separate. Then the bases get new complementary partners. When the partners bond together new strands form.
DNA, RNA and Gene RNA | DNA | Single Strand | Double Helix | Bases are A, U (instead of T), G and C. | Bases are A, T, G and C. |

RNA is a single section of DNA that has been copied. mRNA is a messenger to make proteins.
Sequence of Amino Acids = Proteins
Each 3 bases are called a Codon U | A | G | This makes an Amino Acid.
Some genes are active in every cell, some are not.
Protein Synthesis
DNA separates -> Bases pair (mRNA (T turns To U)) -> mRNA goes to Ribosomes -> Bases make a codon ->makes an Amino Acid -> Amino Acid pairs up in a sequence -> Makes a Protein.
Two Strands in the DNA unzip. mRNA bases pair with the Open DNA bases to form a strand of mRNA -> The mRNA molecule moves out of the nucleus and goes to one of the many Ribosomes.
Plant Growth * Plants have meri-Stem cells – unspecialised cells they are found in the tip of the roots and the shoot tips. * Humans have stem cells – but IN the body they are Stem cells for a particular organ. * However you can manipulate human stem cells when you take them out of the body and you can instruct them to grow into different organs.
How do Plants grow? * Gardeners take cuttings from plants * Some cuttings grow new roots when you put them in water or compost. * Others can grow better when you add auxins – these are plant ‘growth hormones’.
How do Plants Grow?
Phototropism – Plants growing in the direction of light
Photo tropism helps plants live because they need light to live and phototropism helps plants grow in the light, to increase the rate of photosynthesis to create more nutrients (glucose) to help them grow.
At the tip of the shoot are plant hormones (Auxins), the control growth. More auxins are produced on the dark side (diffuse). More Auxins, means more growth and the shoot bends towards the sun. * They do this by releasing a growth hormone called Auxins from the tip of the shoot. * The Auxin will go down one side of the stem and stimulate that side to grow faster than the other side. This will cause the shoot to bend. * It’s a bit like one of your legs growing faster than the other, this would make you bend to one side. * If the tip was covered the shoot would stay straight.
B6 NOTES: Brain and Mind