What are the five components of most animal cells?
Cell membrane, mitochondria, ribosomes, nucleus and cytoplasm
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What does the nucleus do?
Contains DNA in the form of chromosomes
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What does the cell membrane do?
Gives the cell its shape and controls what goes in and out of the cell
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What do the mitochondria do?
Most of the reactions involved in respiration take place in mitochondria
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What do the ribosomes do?
Where proteins are synthesised
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What does the Cytoplasm do?
Where most of the cells chemical reactions happen
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What features do plant cells have that animal cells don't and what do they do?
Chloroplasts -where photosynthesis happens. Vacuole - large internal structure containing sap, salts, sugar and water. Cell wall - supports the cell's structure
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What are cell walls made of?
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Why don't bacterial cells have a 'true' nucleus?
Because they have a single strand of DNA floating in the cytoplasm
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What shape is a DNA molecule?
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What are bases?
Molecules that cross-link the two strands together
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What are the four bases and which ones are paired?
A with T and C with G
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What are nucleotides?
Small groups of molecules that make up the two strands. Each nucleotide contains a base
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Who made the first DNA model in 1953?
Watson and Crick
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What data did they use from other scientists' experiments?
X-rays showing that DNA was a double helix shape made of two chains and other data proving the bases came in pairs as well as their proportions
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Why do many people believe that more scientists should have been included in the Nobel Prize list?
Because a lot of the data Watson and Crick needed was found by other scientists
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Why does DNA need to replicate itself whenever a cell divides?
To make sure the new cell has a full set of chromosomes
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How does DNA replicate itself?
The two strands 'unzip' to separate exposing the bases. Nucleotides floating around the nucleus join onto the bases using complementary base pairing to make two identical strands of DNA
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What is a section of DNA that codes for a specific protein called?
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How many bases code for one amino acid in a protein chain?
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How is a unique protein created?
Each gene contains a different sequence of bases
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Where does protein synthesis happen?
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What molecule carries the genetic code from the nucleus to the ribosome?
messenger RNA (mRNA)
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Briefly evaluate the protein synthesis process
DNA strand unzips and mRNA matches bases; mRNA carries code out of nucleus through cytoplasm to ribosome; mRNA travels through the ribosome which reads the base code; 3 bases codes an amino acid which the ribosome links into a chain to form a protein
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How is a cell's protein synthesis controlled to only make the necessary proteins?
The genes that code for other proteins are 'switched off' meaning their proteins aren't produced
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Why is this necessary? Give an example
Because the cell's function is determined by the proteins that make it up e.g. a muscle cell only needs the genes that code for muscle protein and doesn't need bone or blood proteins to be made
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Give four uses of proteins and an example for each
Enzymes - Amylase. Carrier molecules - haemoglobin. Hormones - insulin. Structural proteins - collagen.
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Give three examples of chemical reactions that happen in cells
Photosynthesis, respiration and protein sysnthesis
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What are enzymes?
Biological catalysts needed to speed up useful reactions in the body without the need for higher temperatures
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Why does every enzyme have a specific shape?
Because they are all coded by specific genes to do specific jobs
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What is the molecule changed in a reaction involving an enzyme called?
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What is an active site?
The part where the substrate joins on
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Why do enzymes have a high specificity for their substrate?
Because they're designed to react with only one substrate which must fit into the active site precisely
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Is the enzyme changed by the reaction?
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How can the substrate(s) be changed during the reaction?
Either one substrate is split into two products or two substrates are combined to make one product
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Why do enzymes have an optimum temperature?
Enough heat to give the particles enough energy to increase the number of successful collisions but not so much that the active site is denatured by the temperature
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What is the optimum temperature for human body enzymes?
37 degrees Celcius
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What other factor affects enzymes' reactions in a similar way to temperature and has an optimum?
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Why does the enzyme Pepsin have a pH of 2 instead of a neutral 7?
Because it has its effect in the stomach acid
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How are enzymes denatured?
High temperature or incorrect pH interferes with the bonds holding the enzymes together which changes the shape of the active site
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What happens if the active site denatures?
The proteins change shape so the substrate doesn't fit into the active site so the reaction stops
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What is a Q10 value?
Shows how much the rate of reaction changes when the temperature is raised by 10 dC
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What is the Q10 equation?
Rate at higher temperature/Rate at lower temperature
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What does a Q10 value of 2 mean?
The rate doubles when the temp. is raised by 10dC
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What are gene mutations and what effects do they have?
A change in the DNA base sequence - can stop the production of a protein or cause another to be produced
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What problems can gene mutations cause if they occur in reproductive cells?
The offspring might develop abnormally or die during early development
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How can gene mutations cause cancer?
Mutant cells being to multiply uncontrollably and spread to other parts of the body
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How do gene mutations cause evolution by natural selection?
Sometimes the new/different protein produced by a mutation can be an improvement. This gene is then passed to the next generation making them more likely to survive and pass on the gene. The gene passes through the species which then evolves
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What two things can increase the risk of mutations?
Ionising radiation and mutagens (chemicals that cause mutations)
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What types of radiation can cause mutations?
X-rays, UV, Gamma and radioactive substances
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Give three advantages of multicellular organisms
Able to be much bigger and travel further; allows cell differentiation to develop cells that do different specific jobs; can be more complex with specialised organs and adaptaions
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What must a multi-celled organism's specialised organ system have?
A system to communicate between cells (e.g. CNS); A system to supply cells with nutrients (e.g. a circulatory system); A system that controls the exchange of substances with the environment (e.g. respiratory system)
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What is Mitosis?
A cell reproduces itself by splitting to form two identical offspring
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What is it used for?
Growth and repair
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How does Mitosis happen?
DNA is replicated; DNA coils into double-armed chromosomes, both arms are identical; chromosomes line up in centre of cell and arms are pulled to opposite poles by cell fibres; membranes form around two sets of chromosomes; Cell divides into two
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What is Meiosis?
Creation of Gametes
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What do the terms Diploid and Haploid mean?
Diploid - a cell with two copies of each chromosome in its nucleus, one from mother and one from father (46 in humans). Haploid - only one copy of each chromosome (23 in humans)
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How does Meiosis happen?
DNA replicates and forms double-armed chromosomes; chromosomes arrange into pairs with info about the same features (23 pairs in humans); pairs split up to form two cells with 23 in each; both cells go through mitosis to make four haploid gametes
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Why does meiosis cause genetic variation?
The gametes produced have a random mixture of the organism's mother's and farther's chromosomes
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What is the diploid cell created by fertilisation called?
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How does fertilisation cause genetic variation?
The zygote will have half its chromosomes from each parent so will have features of both but won't be exactly like either
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How are sperm cells adapted to their function?
They have tails for swimming, lots of mitochondria for energy, they have an acrosome in the head filled with enzymes which break down an egg cell's membrane so the sperm's chromosomes can enter it
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How do plants and animals grow differently?
Animals grow to a finite size then stop, plants can continue to grow until they die. Animals grow by cell division, plants mostly grow by cell elongation
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Where does cell division usually only occur in plants?
Meristems - tips of shoots and roots
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What is Differentiation?
A cell changing to become specialised for its particular job
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What are stem cells?
Undifferentiated cells that ca develop into different types of cell
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Where in the human body can stem cells be found?
In early stage embryos and bone marrow
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Why are bone marrow stem cells not as versatile as embryonic stem cells?
Because they can only develop into certain other cells
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Explain how plants can be cloned easily
All plant cells are undifferentiated so cuttings can be planted and grow into exact genetic copies of the original plant because their cells can develop into all types of cell needed
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How can bone marrow stem cells be used to cure blood diseases?
Bone marrow transplants can synthesise new blood in the body to cure diseases like leukemia and sickle-cell anaemia
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What is stem cell therapy?
Scientists extract stem cells from early human embryos and grow tissue to eventually repair damage e.g. spinal injuries and brain damage
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Why are some people against stem cell research?
Some believe that each embryo used is a potential human life destroyed and think it is unethical
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What is the counter-argument?
People who are already living and are injured should be prioritised over embryos. Also most of the embryos used are unwanted from fertility clinics and would be destroyed otherwise
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Why are there stocks of stem cells around the world?
Scientists need them for research but some countries (like the USA) won't fund work to make more stem cells.
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Is the making of new stem cells for research allowed in the UK?
Yes, but there are strict rules
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Why are there different methods of measuring growth?
Each method has pros and cons and is useful in different ways
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Give and explanation, an advantage and a disadvantage for each of the following growth measurements: Length
Measuring the length/height of a plant or animal. Ad: Easy to measure. Dis: Doesn't tell you about changes in width e.g. diameter of branches
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Weigh the plant or animal as it is. Ad: Easy to measure (depending on size). Dis: Very changeable i.e. a plant will be heavier just after rain fall and an animal will be heavier with a full bladder
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Dry out the organism before weighing it. Ad: Not affected by amount of water in the organism or how much it has eaten. Dis: The organism must be killed beforehand which could be tricky if you're weighing a person ;)
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Which is the best and why?
Dry mass - more comprehensive representation of the organism's size
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What are the five phases of human growth? Describe each
Infancy - rapid growth for approx. two years; childhood - steady growth for approx. 8-10 years between infacy and puberty; adolescence - rapid growth through puberty and body development; maturity/adulthood - growth stops; old age 65 yo to death
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In a baby in the womb the brain grows faster than the rest of the body, why?
Because a large, well-developed brain gives greater survival chances
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What is respiration?
The release of energy from glucose in cells
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What is ATP used for in cells?
Energy currency - it is a means of transferring energy from where it is released by respiration to where it is needed
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Why is the rate of respiration affected by temperature and pH?
Because the reactions are controlled by enzymes
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What are the two types of respiration?
Aerobic and anaerobic
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Give the balanced symbol equation for Aerobic respiration
C6H12O6 + 6O2 ---> 6CO2 + 6H2O + Energy Released
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Why is oxygen consumption used to estimate metabolic rate?
Because when the respiration rate increases, so does oxygen consumption and carbon dioxide production
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When does Anaerobic respiration happen?
When the body cannot supply enough oxygen to your muscles
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Give the word equation for Anaerobic respiration
Glucose ---> Lactic Acid + Energy Released
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Why is Aerobic respiration better than Anaerobic?
Because it releases more energy for every molecule of glucose broken down and doesn't produce lactic acid which fatigues muscles
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What is an oxygen debt?
After stopping exercise, if anaerobic respiration has occurred, the body needs extra oxygen to break down the built-up lactic acid to allow you to respire aerobically again so you continue to breathe heavily for a while
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Where is lactic acid broken down?
In the liver
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Why must the heart-rate remain high after exercise?
To get lactic acid from muscles to the liver quickly
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What is a Respiratory Quotient?
A calculated value to tell if someone is respiring Aerobically or Anaerobically
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Give the RQ equation
Amount of CO2 produced/Amount of O2 used
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What does a RQ of more than 1 mean?
More CO2 is being produced than oxygen used so the person is respiring Anaerobically
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What is blood plasma and what seven things does it carry?
Pale yellow liquid part of the blood carries: Blood cells (Red, white and platelets); water; digested food products (glucose, amino acids etc.); CO2; Urea (from liver to kidneys); Hormones; Antibodies
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What do red blood cells do and how are they adapted to their function?
Carries oxygen around the body - biconcave shape gives large surface area to volume ratio and a large amount of haemoglobin means they can carry lots of oxygen
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Why don't red blood cells have a nucleus?
So there's more room for haemoglobin
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How exactly is oxygen carried?
Haemoglobin combines with oxygen in the lungs (specifically the alveoli) to form oxyhaemoglobin. the reverse happens in body tissue to release oxygen into cells
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Why are red blood cells flexible?
So they can easily pass through narrow capillaries
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What are the three types of blood vessel?
Arteries, Veins and Capillaries
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What is the lumen of a blood vessel?
The hole (tube) in the middle that blood flows through
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Give the properties of an artery and the reasons for them
Thick elastic walls that can expand to accommodate for high pressure, smaller lumen to keep blood pressurised
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Give properties of veins and reasons
Thinner walls than arteries because the pressure is not as high so the lumen is also larger. They also have valves to stop blood flowing backwards, away from the heart
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Very small lumen (sometimes only wide enough for one red blood cell) so very low blood pressure, single cell thick wall that is permeable to allow gas exchange
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Why does the pressure in arteries have to be higher than in veins?
Because the blood has to get all the way around the body before getting back to the heart
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What is a Double Circulatory system?
Blood passes through the heart twice in a full cycle (Heart to lungs to heart to the rest of the body).
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Why do mammals have one?
Mammals have a double circulatory system so blood can be pumped around the body faster at a higher pressure to increase the rate of blood flow. This is useful as mammals use lots of oxygen maintaining body temperature
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What are the four blood vessels that carry blood in and out of the heart and what does each do?
Vena Cava (brings deoxygenated blood from body into heart), Pulmonary Atery (carries blood from heart to lungs to be oxygenated), Pulmonary Vein (carries blood from lungs to heart), Aorta (takes blood from heart to rest of body)
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Describe what happens in the right-hand side of the heart
Deoxygenated blood comes into right Atrium through Vena Cava; Blood moves through tricuspid valve into right ventricle; muscle contracts pushing blood through semiluar valve to lungs through pulmonary artery
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Describe what happens in the left-hand side of the heart
Oxygenated blood comes into left Atrium through pulmonary vein; blood moves into left ventricle through bicuspid valve; muscle contracts pushing blood through semilunar valve into Aorta to the rest of the body at high pressure
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Why does the left ventricle have a thicker wall than the right?
It needs more muscle because it has to pump blood all the way around the body whereas the right only has to pump to the lungs
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Why are the valves needed?
To prevent backflow of blood
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What is selective breeding?
Humans artificially select which plants or animals they're going to breed together to get the desired characteristics
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Give examples of the features that can be obtained through selective breeding
Maximum yield of meat, milk, grain etc.; Good health and disease resistance; Various properties like temperament, speed and attractiveness
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Briefly describe the selective breeding process
Select organisms from stock with the best characteristics; Breed them together; Select the best of the offspring and breed them together; Continue this process for several generations until the traits become strong through the population
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What is the main problem with selective breeding?
It reduces the gene pool - the number of different alleles in a population
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Why does this happen?
Because the 'best' organisms are continuously bred together and they are closely related so there is little genetic variation (there's inbreeding)
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Why can inbreeding cause health problems?
Most harmful genetic diseases are caused by recessive alleles which are more likely to build up in the population if there is inbreeding
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What can happen if a new disease is introduced to an inbred population?
If it kills one of them, it's likely to kill them all as they will all have a similar genetic makeup so there's a smaller chance of resistant alleles
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What is genetic engineering?
Moving genes from one organism to another to make useful products
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What is the main advantage of genetic engineering?
You can produce organisms with new and useful features very quickly
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Why has genetic engineering been used in rice and how?
Populations around the world rely on rice; Rice has very little vitamin A, causing vitamin A deficiency in these populations (other sources are scarce); Scientists put the gene that controls beta-carotene production from carrots in rice; This give vA
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Why and how has genetic engineering been used for insulin production?
Pancreas transplants are rare and pig insulin is expensive but diabetics still need insulin; human insulin production gene put into bacteria; bacteria is cultured in a fermenter; Human insulin extracted from the medium as it is produced by bacteria
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Why and how is genetic engineering used in crops?
Some plants are resistant to herbicides, frost and disease but not most crops; The genes that give plants these features can be put into common crops to increase yield and allow them to grow in different conditions (e.g. in winter)
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What is the main risk of genetic engineering?
The inserted gene can sometimes have unexpected harmful effects
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Give an example
Genes are often inserted into bacteria to produce useful products (like insulin) but if they mutate, the bacteria can become pathogenic. Foreign genes could make bacteria more harmful and unpredictable
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Why are some people worried about DNA 'escaping'?
In theory it can cause weeds to gain rogue genes from crops that have been genetically engineered to be resistant to herbicides meaning weedkillers won't damage them and they could grow uncontrollably
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Describe the genetic engineering process
The gene that causes the desired characteristics is selected; The gene is 'cut' from the DNA using enzymes and is isolated; It is then inserted into into the DNA of the subject organism; The organism replicates and the useful product is produced
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Discuss why some people believe genetic engineering is unethical
Some think it's wrong to change natural organisms just for human benefits if the animal suffers; It could lead to genetic engineering of people to make children with certain features; The future of genetics is unpredictable if changes continue
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What is gene therapy?
Altering a person's genes in an attempt to cure a genetic disorder
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What effect does altering genes of body cells have?
Changes the cells that are most affected by the disorder to have different alleles and cure the disorder. This does not affect gametes so the faulty genes will still be passed on to the offspring
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What effect does altering gametes have?
A change in the gametes' genetics means that every cell in the offspring will have the difference so will not be affected by the disorder, however it does not cure the sufferer
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Which method of gene therapy is illegal and why?
Gene therapy involving gametes - it could cause unexpected consequences meaning all future generations would be affected by new genetic problems. Also, it could lead to the creation of 'designer babies' which many think is unethical
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Clones are genetically identical organisms
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How can you clone an adult animal?
By transferring a cell nucleus into an egg cell
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What was the first mammal to be successfully cloned?
Dolly the sheep
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How was Dolly created?
Egg nucleus removed; diploid nucleus from udder cell of another sheep inserted into egg; cell given electric shock so it started dividing by mitosis; the now embryo was implanted in a surrogate sheep's uterus; clone of the udder cell sheep born
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Give benefits of cloning
Mass production of animals with desired characteristics; Pig organs can be used for transplants and GE combined with cloning could make a constant supply; Cloning adult body cells can produce human embryos for stem cell therapy
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Why are human embryos made by cloning body cells better to use than regular embryos?
Because they have exactly the same genetic information as the patient which reduces the risk of rejection
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What are the risks of cloning animals?
There is some evidence that cloned animals might no be as healthy as normal ones; Since cloning is still quite new, there might be consequences we're not yet aware of
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What ethical issues make human cloning a problem?
Due to an increased number of surrogate pregnancies there would probably be more miscarriages and stillbirths; They may be unhealthy and die early; A human clone could have psychological damage from knowing they are not really individual or natural
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How do you clone a plant?
Plant a cutting
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Why does this work?
Because plant cells keep their ability to differentiate but animals lose this ability earl on. This means cuttings can grow roots
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Describe how are plants commercially cloned by tissue cultures?
Select a plant with desired characteristics; remove several pieces of tissue from shoots and roots; grow tissue in nutritious medium with growth hormones in sterile conditions; Transfer plants to potting compost to continue growth
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Give pros and cons of of commercially used cloned plants
Pros: You can almost guarantee the characteristics, possible to mass-produce plants that are difficult to grow from seeds. Cons: If there is a problem with their environment, all the plants will suffer; lack of genetic variation
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Other cards in this set
What does the nucleus do?
Contains DNA in the form of chromosomes
What does the cell membrane do?
What do the mitochondria do?
What do the ribosomes do?