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Syllabus
removed
2.5 - 2.6 stem cells
2.14 enzyme practical
2.33 food energy practical
2.40 - 2.45 plant gas exchange
2.53 - 2.58 plant transport
2.63 - 2.64 vaccination and clotting in detail
2.70 - 2.79 excretion and the kidney
2.81 homeostasis
2.86 hormone vs. nerves
2.95 ADH, LH, FSH
3.1 - 3.7 plant reproduction
2.86, 2.89, 2.91 - 2.94 Nervous system
4.1 - 4.5 biodiversity and field work
5.12 - 5.20 food production, selective
breeding, GM, cloning
1.1 - 1.4 variety and characteristics of life
2.1- 2.4 cells
2.7 - 2.13 molecules
2.15 - 2.17 movement in and out of cells
2.18 - 2.23 photosynthesis
2.24 - 2.32 diet and digestion
2.34 - 2.39 respiration
2.46 - 2.50 breathing and gas ex.
2.51 - 2.52 principles of transport
2.59 - 2.62 blood
2.65 - 2.69 heart and circulation
2.80 - 2.82 response to stimulation
2.83 - 2.85 plant tropisms
2.87, 2.88, 2.90 - 2.94 Nervous system
3.8 - 3.13 human reproduction
3.14 - 3.39 inheritance and evolution
4.6 - 4.9 food chains
4.10 - 4.11 carbon and nitrogen cycles
4.12 - 4.18 pollution

Breathing and Gas Exchange
Name and describe all the organs
1. Larynx, trachea and rings of Cartilage
protects lower airways. where air goes through. rings of cartilage prevent the trachea from closing
2. Bronchi, Bronchioles and Alveoli
air splits through all these different pathways, the smallest being the alveoli, where gas exchange occurs
3. Pleural membranes and Pleural fluid
pleural membranes surround the lungs, and it’s protected from sticking into the ribcage by the pleural fluid surrounding them
4. Diaphragm, intercostal muscles and ribs
Diaphragm and intercostal muscles expand and contract to change the volume capacity of the lungs, causing breathing. the ribs protect the lungs from being damaged
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Understand the role of the intercostal muscles and the diaphragm in ventilation
BIDEC
Breathe In Diaphragm and External Contract
BODER
Breathe Our Diaphragm and External Relax
Alvioli Adaptations
1. moist, allows gas exchange to occur
2. number of them gives for more surface area
3. one cell thick, short distance for diffusion
4. good supply of blood and oxygen to maintain diffusion gradient
Effects of Exercise in breathing and the release of carbon dioxide
exercise means that more glucose needs to be used for energy, meaning there is a higher demand for oxygen to release the energy. Breathing rates increase to receive more oxygen, turning it into carbon dioxide through respiration. since respiration rates are higher, the release of carbon dioxide also increases
How to carry out an experiment about the release of CO2
breathe through a tube connecting two test tubes. lime water is placed in both. the test tube where air enters remains clear, while the test tube where air goes out turns cloudy - a positive result for the presence of carbon dioxide.
Effects of Smoking (4)
1. Increase of risk of pulmonary infections
tar damages the cilia and mucor. these two cells produce mucus to trap pathogens and sweep them down the the stomach to be killed by the acidity.
2. Emphysema
the breakdown of alveoli reduces surface area, thus making it harder for gas exchange to occur and obtain oxygen.
3. RISK OF CORONARY HEART DISEASE
carbon monoxide binds with the red blood cells, not allowing the oxygen to bind. heart rate increases to make up for the lack of oxygen, which can damage capillaries and increase the risk of coronary heart disease
4. CANCER
contains radioactive substances that increase the risk of mutations
Food and Digestion
Describe the digestive system
Mouth and Salivary Glands
teeth break down the food so it can be swallowed and increases surface area so it can be digested quicker. moist also helps it travel down the oesophagus
salivary glands secrete AMYLASE to break down starch
Oesophagus
tube through which the food travels, is elastic and contains muscles to push it downwards
Stomach, pancreas
stomach is very acidic, kills all pathogens, bacteria. pancreas secrete protease, an enzyme which digests protein, whose optimum PH is 2 due to its acidity
Gall Bladder, Duodenum (small intestine)
gall bladder produces bile, which neutralises the food from the stomach as it is acidic as it is alkaline. it also emulsifies fat into smaller droplets in order to increase surface area to make the enzymes work more quickly. Lipase and other enzymes are excreted from the pancreas
Ileum lining
containing villi, one cell thick lining in the ileum covered by microvilli in order to increase surface area. have blood capillaries inside to shorten the distance of the nutrients and the blood, then transferred into the entire body. also contain mitochondria to move and match the concentration gradient, facilitating diffusion through active transport
Large intestine and rectum
absorption of remaining water to create a solid feces of undigested material, then excreted through the rectum.
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Elements present in carbohydrates, proteins and lipids
hydrogen, carbon, OXYGEN for both carbs and lipids,
protein is made of amino acids » hydrogen, carbon, oxygen, nitrogen and sulfur
lipids » GLYCEROL AND FATTY ACIDS
Tests for Starch, Glucose, Protein, Lipids
Starch
add iodine, initially orange, later turns BLUE BLACK
Glucose
add BENEDICT SOLUTION, from blue to BRICK RED
Protein
add BIURET TEST, forming PURPLE
LIPID
add ETHANOL, forming a CLOUDY WHITE LAYER
Identify the sources and uses of carbs, lipids, proteins, vitamins A, B, C and D, mineral ions, water and dietary fibre
Carbs
used for obtaining energy, found in wheats
Protein
used for the growth and repair of tissues, found in animal products and beans
Lipids
used to store in the body? found in avocados and nuts
Vitamin A
used to prevent night blindness, helps with the retina. found in carrots
Vitamin B
used to prevent beri beri, found in meat and veggies
Vitamin C
used to prevent scurvy, found in fruits and vegetables.
Vitamin D
used to prevent rickets, source from sunlight
Iron
helps the hemoglobin bond with the oxygen in red blood cells, preventing anemia. found in meat
Calcium
helps preventing rickets and weak bones, found in dairy
Water
needed by many parts of the body, including the brain.
Dietary fibre
helps with digestion, cellulose and found in most plants
How is food moved through the gut
a process called peristalsis in the walls of the gut,
the longitudinal muscles (external ) and circular muscles (internal ) contact and expand in order to move food along the gut
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Coordination and Response
Understand how organisms are able to respond to their environment
through the nervous system: based on the brain, spinal chords and nerves that perceives and reacts to changes in the environment
What does a coordinated response look like and what is the central nervous system
stimuli » receptor neuron » COORDINATION CENTER » motor neuron » effector
KEY DEFINITIONS
stimulus: any perceivable change in the environment
receptor: organs in the body that are able to perceive the environment. eg skin, eyes, ears, nose, mouth
effector: muscles, organs that are able to move accordingly to respond to its environment
coordinating center (CNS): involves the brain and the spinal cord, where neurons fire
type of neurons:
- receptor neurons CONVERT STIMULI INTO AN ELECTRICAL IMPULSE
- motor neurons
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describe the function, structure and adaptation of a simple reflex arc.
adapted to make the response faster, automatic and protective, thus avoiding danger.
does not involve the coordination of the brain
stimulus » receptor neuron » relay neuron » motor neuron » effector
Blood and circulation
Why can unicellular organisms can rely on diffusion
they have a high surface area to volume ratio, meaning their nutrients can diffuse easily through the entire cell. larger beings have a low surface area to volume ratio, thus a need for a transport system, as diffusion is not efficient enough
The structure of the circulation and heart
double circulatory
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VEINS = from the body to the heart
ARTERY = from the heart to the body
involving:
- pulmonary artery and vein
- vena cava and aorta,
- renal artery and vein
- hepatic artery and vein
Heart contains:
1. two ventricles (bottom)
2. two atria (top)
(4 chambers)
3. Valves
CARDIAC MUSCLE contracts and expands in order to pump the heart.
Factors that may cause Coronary heart disease
1. smoking
2. lack of exercise
3. hereditary and genetic
4. stress
5. diet
6. high blood pressure
Effect on heart rate of adrenaline and exercise
exercise demands more oxygen for the muscles in order to break down the glucose for energy.
the heart will have to obtain oxygen by the lungs at a faster rate, thus raising heart beat.
secretion of adrenaline for the adrenal glands also causes a quicker fast rate, as it helps the body be prepared for a fight of flight response.
controlled by the MEDULLA
How the structure of capillaries, arteries and veins relate to their function
Arteries
thick muscle and elastic tissue
to stretch and recoil to support high blood pressures. to control the blood flow by widening or contricting
Veins
thin muscle and elastic tissue, containing valves
no need for thick muscles due to low blood pressure, valves prevent it from going backwards
Capillaries
one cell thick
provides a very short distance for diffusion as it is close to every cell in an organ
Describe the Composition of Blood
1. Plasma
Liquid part of the blood: carries nutrients, other blood components, urea, hormones, HEAT
2. Red Blood cells
carry oxygen. adaptations:
- small, can squeeze through tiny capillaries
- hemoglobin binds with the oxygen to form oxyhemoglobin
- no nucleus gives more space for the hemoglobin
- biconcave shape, squeeze
3. White blood cells
designed to eliminate pathogens and protect the body
4. Platelets
parts of other cells that are broken, serve to close open wounds. Blood clotting: prevents blood loss and entrance of pathogens.
How does the immune system respond to infection using white blood cells and how do vaccines work.
1. two types of white blood cells: Lymphocytes and Phagocytes.
2. Phagocytes change their structure in order to surround and digest the pathogen
3. lymphocytes produce antigens to bond with the pathogen’s antibody.
it can take several days for the lymphocytes to find or produce the correct antigen to the specific antibody.
once it’s found the lymphocytes reproduce rapidly. also produces memory cells.
on a second infection of the same pathogen, the white blood cells will be able to eliminate all of them at a much faster rate and a greater quantity
Vaccines give a weak or dead version of a pathogen that won’t cause a lot of damage. The white blood cells are forced to produce antigens and memory cells, a process that may take several days. Once the body comes into contact with the real pathogen, the lymphocytes will produce the antigens at a faster rate and greater quantity.
Reproduction in Humans
Difference between sexual and asexual reproduction
sexual reproduction involves the fusion of a female gamete with a male gamete
asexual reproduction does not involve the fusion of a female gamete and a male gamete
Define Fertilization
the fusion of the female gamete nucleus with the male gamete nucleus to produce a zygote
The zygote then undergoes cell division through mitosis to produce an embryo
The structure of the male and female reproductive system.
· MALE
testis
where sperm is produced
sperm duct
muscular tube where the spect travels from the testis towards the urthera
uthera and glands
where sperm travels from the sperm duct towards the penus
the glands secrete liquid that is added to the sperm to produce semen
erectile tissue, penus, foreskin
erectile tissue swells with blood to make the penus erect
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· FEMALE
vulva and vagina
where the sperm is deposited
cervix
the neck of the uterus
uterus / womb
where the baby begins to be produced.
Endometrium and Muscular uterus wall
endometrium is the lining of the uterus, with good blood supply in order and stretchy to host the baby
Muscular uterus wall
Oviduct and ovaries
ovaries produce female gametes every 28 days
these travel down the fallopian tube (oviduct), where it meets with the male gamete to fuse. If fusion happens, it will be implanted in the endometrium
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Name the secondary sexual characteristics
FEMALE
- growth of breasts
- pubic hair and armpit hair
- widening of hips
- periods
MALE
- enlargement of penus
- pubic, armit and facial hair
- muscular
- deepening of voice

Describe the menstrual Cycle
Ovulation is the release of ripe female gamete (egg) from the ovary
1. FSH
produced in the pituitary gland
triggers the development of the egg in the ovary
triggers the production of Oestrogen in the ovaries
2. Oestrogen
triggers the thickening of the lining of the ovary
triggers the pituitary gland to stop producing FSH
triggers the production of LH
3. LH
triggers the release of the egg into the oviduct (DAY 14)
triggers the production of progesterone in the ovary
the male and female gamete will fuse 1/3 into the oviduct
4. Progesterone
maintains the lining of the ovary thick in case the zygote needs to be implanted
stops the pituitary gland from producing more LH and FSH
falls if there is no fertilization. the fall in progesterone and oestrogen levels causes the lining of the uterus to break, thus causing a period.
if fertilization occurs, the placenta will maintain the production of progesterone and oestrogen
Explain the role of the placenta in pregnancy
-
placenta: an organ that develops during pregnancy in order to provide nutrients and oxygen to the baby
gametes » zygote » embryo » fetus
thousands of cells in the ovaries are potential eggs. FSH triggers the development of one of these eggs into a Follicle
adaptations
1. increased surface area by villi
2. the maternal blood never comes into contact with the baby’s blood (it is dangerous because the mother’s body may interpret the baby’s blood as a pathogen, thus killing it)
3. the embryo is protected by AMNIOTIC FLUID surrounded by AMION MEMBRANE to prevent the contact between the blood of the baby and the blood of the mother and protects against bumbs
4. good supply of the maternal blood keeps the concentration gradient (nutrients, exchange of urea, co2 and o2 in the umbilical chord
UMBILICAL VEIN
away from the mother’s heart, towards the baby, carries the oxygen and nutrient rich blood
UMBILICAL ARTERY
towards the mothers heard, away from the baby, carries urea and co2
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Plants and Food
Required Practical: testing for production of starch

KEY POINT:
carbon dioxide + water » glucose + oxygen
1. place leaf in boiling ethanol to remove the chlorophyll
2. wash in cold water to soften
3. add iodine, blue black colour tests positive
note this will only work if the plant has had the chance to photosynthesise, thus it must have had some hours of sunlight before the test.
Required practical: investigate the need for light, carbon dioxide, chlorophyll and water FOR PHOTOSYNTHESIS
INVESTIGATING THE NEED FOR LIGHT
1. set the plant in a dark room for some days
2. test for starch with iodine
plants need light, so iodine will test negative for presence of starch.
INVESTIGATING THE NEED FOR CARBON DIOXIDE
1. set the plant in a closed bell jar with sunlight, water and all other control variable
2. place soda lime in the bell jar (it absorbs all the carbon dioxide)
3. test for starch
INVESTIGATING THE NEED FOR CHLOROPHYLL
1. the same test as for starch: removing the chlorophyll using boiling ethanol and leaving the plant for a few days will mean it will not be able to produce stach
INVESTIGATING THE NEED FOR WATER
1. give the plant an isotope of oxygen in water (H2O)
2. “track” the isotope to see if it appears in the photosynthesis products
we can’t deprive a plant from water, because it is needed for many other functions other than photosynthesis so it will die.
Required practical: test for oxygen as a product of photosynthesis
1. set an underwater plant on a beaker full of water.
2. collect the gas with a test tube
3. test the gas for oxygen using a glowing splint
Note: this practical can also be used to investigate the rate of photosynthesis at different light intensities.
Word and Symbol equation for photosynthesis
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Describe the structure of the leaf and its adaptations for photosynthesis
1. Cuticle
waxy layer on the top section of the plant. prevents any water loss EVAPOTRANSPIRATION and acts as a barrier to pathogens
2. Upper Epidermis
contains few or no stoma. is also relatively transparent to allow the palisade to receive sunlight
3. PALISADE CELLS
contains lots of chlorophyll to photosynthesise, is found in the upper section of the leaf to receive sunlight
4. SPONGY CELLS
form gaps of air where gas exchange happens
Note: MESOPHYLL LAYER IS MADE OF THE PALISADE AND SPONGY CELLS
5. LOWER EPIDERMIS
site of gas exchange. contains important cells of STOMATA and GUARD CELLS, which changes its shape to open and close to prevent the water loss.
6. XYLEM AND PHLOEM
xylem transports water and minerals from the roots, forming part of the transpiration system.
phloem transports the products such as sugars
correlation between gas exchange and photosynthesis and TEST FOR CO2 CONCENTRATION (triple only)
respiration occurs constantly
photosynthesis occurs at certain times.
if photosynthesis rates are higher than respiration (midday sunlight) , the pant will we uptaking more carbon dioxide than oxygen
is respiration rates are higher than photosynthesis (midnight darkness), the plant will not be producing oxygen, so co2 levels will rise.
test: hydrogen carbonate reacts will co2. high concentration is yellow, normal concentration is orange and low concentration is purple. set three test tubes with different light intensities with hydrogen carbonate
Factors affecting photosynthesis
1. light intensity
2. concentration of co2
3. temperatures
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why isn’t the curve linear? the plant’s photosynthesis rate increases as you give them their optimum temp, light intensity ect. but stop increasing as they have another LIMITING FACTOR
Mineral ions needed in the soil
Magnesium to make chlorophyll
nitrate ions to make amino acids (protein)
Transport in plants (2.15 and 2.17 only)
define diffusion, osmosis and active transport
Diffusion: the net movement of particles from high to low concentration
Osmosis: the net movement of water particles from high concentration to low concentration through a partially permeable membrane
Active Transport: the net movement of particles from LOW TO HIGH concentration which requires energy from the organism (eg. transport in the ileum)
Factors affecting diffusion
1. concentration gradient (higher means quicker)
2. distance
3. heat.
4. Surface area to volume ration
Required practical: investigating osmosis
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Plant Tropisms
Tropism : a response to a stimulus
A positive tropism in which the response goes TOWARDS the stimulus A negative tropism in which the response goes AWAY from the stimulus
Auxin is a hormone which responds to stimulus with growth in the tip of the coleoptile
Phototropism A response to light. plant moves towards the light in order to increase photosynthesis. The plant contains photo receptors, the auxin gathers in the opposite side to the light. Auxin makes the cellulose (a cage that inhibits growth) very loose. this stimulates growth.
Geo tropism A response to gravity, in the roots, towards the stimulus, a positive tropism. In the coleoptile, it grows away from the stimulus, a negative tropism.
Practice Question : Explain plant responses to stimuli
Tropism is a response to a stimulus. Auxin is responsible for responding to stimuli
Phototropism is a response to light. If light comes through only once side, the light receptors in the plant allow for the auxin to accumulate in the opposite side to light in the coleoptile, the tip of the plant's shoot. Auxin stimulates growth, as it makes the plant cell wall, the cellulose, loose and allows for growth. Over time this causes the plant to grow towards the light - a positive tropism
Geo tropism is a response to gravity. the roots grow towards gravity, as auxin accumulates in the underside. This occurs too
Why do some biologists not consider auxin a hormone?
it is not produces in a specific tissue
auxin is a trigger to pre set system, making different consequences it does not have a specific function
Plant growth substances stimulate root growth from a cut stem Describe an investigation to find the best concentration of plant growth substances to stimulate root growth.
CORMS
Ecology and the environment
4.6 Trophic Levels
1. Producer: plants which photosynthesise to convert light to chemical energy (food)
2. Primary consumers: organism which feeds by the producer
3. Secondary consumer: organism which feeds by the primary consumer
4. Decomposer organisms which break down the dead material and help recycle nutrients
Food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer
FOOD CHAINS
show the flow of energy from the sun to the last consumer.
Hence, arrows are pointing right »»»
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FOOD WEBS
a more detailed way to show an ecosystem and how energy flows
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PYRAMIDS OF NUMBER
they don’t have to be pyramid-shaped!! eg. a single tree may feed thousands of ladybugs
PYRAMIDS OF BIOMASS
are usually if not only pyramid-shaped
PYRAMIDS OF ENERGY
always pyramid shaped
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YOU MAY BE ASKED TO DRAW A PYRAMID
Transfer of energy along a food chain
only 10% of the energy is transferred along each trophic level
why?
1. heat loss or energy loss
2. energy transferred to make non digestible material (such as bones)
3. not all the energy from the food is absorbed (feces)
4. not all is eaten
this is why most of the food chains are 3-4 organisms long:
if plants are 100% of the energy, this transfers to 10% » 1% » 0.1%
animals who are tertiary consumers don’t obtain much energy
Draw the Carbon cycle
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photosynthesis fixes carbon into organic molecules such as carbohydrates
these are eaten by animals and other organisms which respire them.
carbon in dead organisms is broken down and released to the atmosphere again
fossilisation of plants and dead organisms are then burnt and released into the atmosphere again
note there is also an ocean uptake of the carbon
Draw the Nitrogen cycle (triple only)
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DECOMPOSERS (bacteria)
Nitrogen fixing
from the atmosphere to the soil
Denitrifying
from the soil to the atmosphere (a process called denitrification)
Nitrifying
turns AMMONIUM IONS into NITRATES which the plants use (a process called nitrification)
Decomposers
turns proteins into ammonium ions
consequences of pollution of air by sulfur and carbon dioxide
sulfur dioxide is acidic, causing acid rain
damages ecosystems, it changes the ph of lakes which can be fatal for organisms
damages infrastructure
makes soil infertile and damages the minerals, no more trees

carbon dioxide is a greenhouse gas, meaning it retains heat
although it is natural and essential to maintain heat during night time, its excess leads to global warming.
the melting of the arctic causes sea levels to rise
the melting of the antarctic does not cause sea levels to rise, but does extinct species such as the polar bear, seals and penguins
disrupts the carbon cycle
other greenhouse gasses and human activity
Water vapour
Carbon dioxide
Methane
Nitrous oxides

human activities leading to global warming:
burning fossil fuels
maintaining cows
mass production and no re/up cycling such as plastic, clothes
killing trees and plants (the only way that carbon is taken away from the atmosphere)
use of CFCs in refrigerators
nitrous oxides in fertilizers and car fuels, and sewage
biological consequences of water pollution sewage and fertilizers
is a good source of food for decomposing bacteria, so they reproduce quickly. they take up all the oxygen of the water, leaving none left for the rest of the animals, thus killing them.
EUTROPHICATION
occurs with both fertilizers and sewage
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effects of deforestation. (triple only )
1. LEACHING
deforestation means that trees don’t take up the nutrients and minerals. such minerals and nutrients are washed away by the rain, causing the soils to become infertile
2. SOIL EROSION
roots of the trees help prevent erosion from the rain in the soil
3. EVAPOTRANSPIRATION
no trees to evapotranspirate water vapour means less formation of clouds, thus less precipitation (rain)
4. CARBON CYCLE
disrupted - more carbon in the atmosphere
5. LACK OF BIODIVERSITY AND DISRUPTION OF ECOSYSTEMS
Inheritance and Evolution
Chromosomes, Genes and DNA
Definitions and Locations for DNA, RNA, Genes, genome and Chromosomes
Genetic materia (DNA) is found in the nucleus of a cell
DNA:
a double helix structure containing the genetic information for all cells
two strands coiled to form a double helix, linked by the bases Adenine, (a) thymine (T), Cytosine (C) and GUANINE (G)
RNA:
single stranded containing uracil (U) instead of Thymine (T)
CHROMOSOME:
tightly packed dna. Humans have 23 pairs of chromosomes
GENES
section of the chromosome containing instructions for the production of particular proteins
alternate forms of the same gene are called alleles such as the gene coding for blue, brown eyes.
GENOME
the complete set of genetic material of an organism
Definitions diploid and haploid
Diploid » containing 23 pairs
Haploid » containing 23
all cells are diploid EXCEPT for gamete cells, which are haploid due to their division of Meoisis, which then fuse to create the 23 pairs.
Protein Synthesis
Describe the process of protein synthesis. (triple only)

Key points to remember:
DNA codes with CODONS which are triplets of the bases A adenine, T Thymine, G guanine and C cytosine
A and T are complimentary. G and C are complimentary
RNA is a single strand containing uracil U instead of T Thymine
Ribosomes are OUT of the nucleus

Protein synthesis is the process of reading the dna to convert it into amino acids
step one: TRANSCRIPTION
only occurs to sections of DNA at a time - a single gene at a time
takes place in the
rna polymerase (enzyme) binds just before the beginning of the gene
formation of Mrna (messenger RNA) which is complimentary to a strand of DNA, forming a single strand and replaces all the thymines with uracil
once the transcription is completed the rna polymerase detaches from the DNA, the Mrna is free to leave

step two: TRANSLATION
occurs in the ribosomes
produces a protein out of the sequence of amino acids
TRNA contains an anticodon, which is a sequence of triplets that are complimentary to the the MRNA, and an AMINO ACID
different TRNA’s bind with the MRNA, setting the amino acids in a specific order
once the sequence is complete the TRNA detaches and leaves a chain of amino acids behind.
Mutations

Mutations
alteration of the DNA base sequence. this can happen in the dna or in the mrna (transcription) when it happens in the dna, it is likely to have a long lasting effect, as the wrong dna will be transcribed several times.
Amino acids sequences are very important in order to make 3D shapes to carry out their functions. Mutations can result in alterations in the amino acid sequence, resulting in the inability to complete its function
Single Base mutations
one base of the amino acid
mutations rarely cause an effect on the phenotype
however some do (eg. Cancer)

Types of errors during protein synthesis
Addition TAG CGA TTA TAG CCC GAT T
Deletion:

Mutagens: external factors that increase the likelihood of mutations
carcinogens (found in tobacco)
radiation (x rays, gamma rays, ultraviolet )

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Mitosis and Meiosis
Why do we need the division of cells?
growth and repair
production of specialized cells
sexual reproduction
genetic variation
Mitosis
each chromosome duplicates itself.
it then divides
genetically identical: the number of chromosomes is preserved from the original to the final one
occurs in every cell division except for the reproductive cells.
growth, repair, asexual reproduction and cloning
Meiosis
this is for the process of fertilization, hence it halves the number of chromosomes into 23 called a reduction division
cell division used for the formation of gametes (sex cells) produced in the testies and the ovaries
every chromosome makes a copy of itself.
right before the first division, there is a mixing of the DNA, to increase the genetic variation.
the fusion of dna of two different parents also promotes genetic variation
main difference: meiosis divides two times, and the division is not by a halve, but a division of "pairs" the separation of the copies occurs in the second division

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Genes and Inheritance

definitions: Heterozygous, Homozygous, allele, phenotype and genotype. (CODOMINANCE for triple only)
Phenotype
the physical characteristics (genes + environment)
most phenotype characteristics are a result of Polygenic inheritance, aka the result of several genes’ expressions. for example skin colour is controlled by several genes, while sex is only controlled by one.
Genotype
the genetic characteristics (only genes)
Allele
a variation of the same gene (Aa)
a dominant allele is one that will transfer into the phenotype (physical characteristics) if it is heterozygous and given a capital letter
while a recessive allele will not transfer into the phenotype unless homozygous, given a small letter
Heterozygous
two different alleles (AB)
Homozygous
two same alleles (AA)
homozygous dominant - have the same dominant allele
heterozygous recessive - have the same recessive allele
CODOMINANCE
pattern of inheritance where neither allele is is dominant, so both alleles are expressed
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Genetic diagram used for probability:
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Monohybrid vs Polihybrd
Family Pedigree diagrams.
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questions involving pedigree diagrams will usually give information of recessive and dominant alleles necessary for a characteristic. EG, the question will say “the gene for polydactyly is recessive rr”
carriers of polydactyly are usually expressed as half a shade in the pedigree diagram . They contain the gene for polydactyly but it is not expressed, as it is recessive
people with polydactyly will be expressed as a full shade. they have homozygous recessive
people without any genes of polydactyly are white.
. The offspring inheritance can be deduced
Determination of sex is in one of the chromosomes:
XX in a female, XY in a male
Natural Selection and Evolution
Explain Darwin’s theory of Natural Selection
process where certain individuals are more adapted and hence have more change of survival in a certain environment. thus, their genes are more likely to spread, resulting in a slow change of characteristics in a species of a specific environment
Understand how resistance to antibiotics an increase in bacterial populations
Antibiotica are chemicals that kill bacteria.
Resistance to an antibiotic first begins with a random mutation that causes the bacteria to be better adapted.
the new antibiotic-resistant bacteria is at an advantage to the other non-resistant bacteria, thus it is more likely to reproduce.
each offspring is born with the genetic variation that allows it to be resistant, thus reproducing even further, while the non resistant bacteria die
eventually all the bacteria from that species are resistant, and the antibiotic is no longer effective.

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