biology 3 ocr gateway continuations cards 15-33

DNA REPLICATTION

• DNA HAS TO REPLICATE ITSELF PRIOR TO CELL DIVISION SO EACH NEW CELL HAS FULL AMOUNT OF DNA
• DNA DOUBLE HELIX 'UNZIPS' - FORMS TWO SINGLE STRANDS
• NEW NUCLEOTIDES (FLOATING FREELY IN NUCLEUS) JOIN ON USING COMPLIMENTARY BASE PAIRINGS - MAKES EXACT COPY OF DNA ON OTHER STRAND
• RESULT - TWO DOUBLE STRANDED MOLECULES OF DNA IDENTICAL TO ORIGIONAL MOLECULE OF DNA

MITOSIS - WHEN A CELL REPRODUCES ITSELF BY SPLITTING TO FORM TWO IDENTICAL OFFSPRING

• HAPPENS WHEN YOU WANT IDENTICAL CELLS E.G. GROWTH
• BEFORE IT STARTS, DNA IS REPLICATED
• DNA COILS UP INTO DOUBLE ARMED CHROMOSOMES - BOTH ARMS CONTAIN EXACT SAME INFORMATION
• CHROMOSOMES LINE UP IN CENTRE OF CELL - DIVIDE AS CELL FIBRES PULL THEM APART - TWO ARMS OF EACH CHROMOSOME GO TO OPPISITE POLES (ENDS) OF CELL 
• MEMBRANES FORM AROUND NEW SETS OF CHROMOSOMES

CYTOPLASM DIVIDES - TWO NEW CELLS WITH THE EXACT SAME GENETIC MATERIAL

MEIOSIS - TYPE OF CELL DIVISION WHICH CREATES GAMETES

• GAMETES - SEX CELLS - EGGS AND SPERM - FORMED BY MEIOSIS IN THE OVARIES AND TESTES 
• DIPLOID - BODY CELLS - EACH OF THE ORGANISMS BODY CELLS HAVE TWO COPIES OF EACH CHROMOSOME IN IT'S NUCLEUS - ONE FROM MUM, ONE FROM DAD
• HAPLOID - GAMETES - ONLY HAVE ONE COPY OF EACH CHROMOSOME - EGG AND SPERM COMBINE TO FORM DIPLOID NUMBER OF CHROMOSOMES          look below  PROCESS OF MEIOSIS

• DNA REPLICATES ITSELF, CURLS UP INTO DOUBLE ARMED CHROMOSOME (LIKE MITOSIS)
• CHROMOSOMES ARRANGE THEMSELVES INTO PAIRS - HUMANS HAVE 23 PAIRS OF CHROMOSOMES - 46 ALTOGETHER - BOTH CHROMOSOMES IN A PAIR CONTAIN INFORMATION ABOUT SAME FEATURES, ONE FROM MUM AND ONE FROM DAD
• FIRST DIVISION - PAIRS SPLIT UP - CHROMOSOMES IN EACH PAIR MOVE TO DIFFERENT POLES OF CELL - IN EACH OF THE TWO NEW CELLS THERE ARE NO PAIRS - MIXTURE OF MUM AND DADS CHROMOSOMES - 23
• SECOND DIVISION - LIKE MITOSIS - CHROMOSOME SPLITS IN HALF - ONE ARM ENDS UP IN EACH NEW CELL
• FOUR NEW CELLS - TWO AFTER FIRST DIVISION, EACH OF THOSE SPLIT AGAIN - CELLS GENETICALLY DIFFERENT - CHROMOSOMES GET SHUFFLED UP - EACH GAMETE GETS HALF AT RANDOM

GENETIC VARIATION

• FERTILISATION - MALE AND FEMALE GAMETES COMBINE TO FORM DIPLOID CELL - ZYGOTE
• CHARACTERISTICS OF ZYGOTE CONTROLLED BY COMBINATION OF GENES ON IT'S CHROMOSOMES
• ZYGOTE INHERITED CHROMOSOMES FROM BOTH PARENTS - SHOW FEATURES OF BOTH PARENTS BUT WON'T BE EXACTLY LIKE EITHER OF THEM

ADAPTATIONS OF SPERM CELL

• FUNCTION - TRANSPORT MALES DNA TO FEMALE EGG
• SMALL AND HAVE LONG TAILS - SWIM TO EGG
• LOTS OF MITOCHONDRIA - PROVIDE ENERGY NEEDED TO SWIM DISTANCE
• ACROSOME AT FRONT OF HEAD - RELEASE ENZYMES NEEDED TO DIGEST WAY THROUGH MEMBRANE OF EGG CELL

BLOOD PLASMA - PALE YELLOW LIQUID WHICH CARRIES EVERYTHING THAT NEEDS TRANSPORTING AROUND BODY:

• RED BLOOD CELLS, WHITE BLOOD CELLS (IMMUNITY) AND PLATELETS (USED IN BLOOD CLOTTING)
• WATER
• DIGESTED FOOD PRODUCTS LIKE GLUCOSE AND AMINO ACIDS FROM GUT TO BODY CELLS
• CARBON DIOXIDE - FROM BODY CELLS TO LUNGS
• UREA FROM LIVER TO KIDNEYS WHERE IT IS REMOVED IN URINE
• HOURMONES - ACT LIKE CHEMICAL MESSENGERS
• ANTIBODIES - PROTEINS INVOLVED IN BODY'S IMMUNE RESPONSE

RED BLOOD CELLS - CARRY OXYGEN FROM LUNGS TO ALL CELLS IN BODY

• SMALL, BICONCAVE SHAPE - LARGE SURFACE AREA TO VOLUME RATIO FOR ABSORBING/RELEASING O2
• CONTAIN HEAMOGLOBIN - GIVES BLOOD COLOUR - CONTAINS IRON - COMBINES WITH OXYGEN IN LUNGS TO BECOME OXYHEAMOGLOBIN - REVERSE HAPPENS IN BODY CELLS TO RELEASE OXYGEN
• NO NUCLEUS - MORE SPACE FOR HEAMOGLOBIN - CARRIES MORE OXYGEN
• VERY FLEXIBLE - EASILY PASS THROUGH TINY CAPILLARIES

ARTERIES - CARRY BLOOD AWAY FROM HEART

• HEART PUMPS BLOOD OUT AT HIGH PRESSURE - ARTERY WALLS STRONG AND ELASTIC TO COPE WITH IT
• WALLS ARE THICK COMPARED TO SIZE OF LUMEN 
• WALLS CONTAIN THICK LAYERS OF MUSCLE TO MAKE THEM STRONG                                                 CAPILLARIES - INVOLVED IN EXCHANGE OF MATERIALS AT TISSUES

• ARTERIES BRANCH ONTO CAPILLARIES - REALLY TINY - TOO SMALL TO SEE
• USES - CARRY BLOOD REALLY CLOSE TO EVERY CELL TO EXCHANGE SUBSTANCES WITH THEM
• SUPPLY FOOD AND OXYGEN AND TAKE AWAY WASTES LIKE CO2 
• ADAPTIONS - PERMEABLE WALLS - SUBSTANCES CAN DIFFUSE IN AND OUT
• WALLS ONE CELL THICK - ICREASES RATE OF DIFFUSION BY DECREASING DISTANCE OVER WHICH IT OCCURS                                                                                 look below  VEINS - CARRY BLOOD TO THE HEART

• CAPILLARIES JOIN UP EVENTUALLY TO FORM VEINS
• BLOOD AT LOWER PRESSURE IN VEINS - WALLS NOT AS THICK - BIGGER LUMEN THAN ARTERIES - HELP BLOOD FLOW DESPITE LOWER PRESSURE - VALVES - KEEP BLOOD FLOWING RIGHT WAY

DOUBLE CIRCULATORY SYSTEMS

• FIRST SYSTEM - CONNECTS HEART TO LUNGS - DEOXYGENATED BLOOD PUMPED TO LUNGS TO TAKE IN OXYGEN - BLOOD RETURNS TO HEART
• SECOND SYSTEM - CONNECTS HEART TO REST OF BODY - OXYGENATED BLOOD PUMPED OUT TO BODY - GIVES UP OXYGEN - DEOXYGENATED BLOOD RETURNED TO HEART TO BE PUMPED TO LUNGS AGAIN

ADVANTAGES - RETURNING BLOOD TO HEART AFTER BEING OXYGENATED MEANS IT CAN BE PUMPED TO REST OF BODY AT MUCH HIGHER PRESSURE - INCREASES RATE OF BLOOD FLOW TO TISSUES - MORE OXYGEN DELIVERED TO CELLS - IMPORTANT FOR MAMMALS - USE UP A LOT OF OXYGEN MAINTAINING BODY TEMP

THE HEART

• RIGHT ATRIUM RECEIVES DEOXYGENATED BLOOD FROM BODY THROUGH VENA CAVA
• DEOXYGENATED BLOOD MOVES THROUGH RIGHT VENTRICLE WHICH PUMPS IT TO LUNGS THROUGH PULMONARY ARTERY
• LEFT ATRIUM RECEIVES OXYGENATED BLOOD FROM LUNGS THROUGH PULMONARY VEIN
• OXYGENATED BLOOD MOVES THORUGH TO LEFT VENTRICLE WHICH PUMPS IT AROUND WHOLE BODY VIA AORTA
• LEFT VENTRICLE - MUCH THICKER WALL THAN RIGHT VENTRICLE - NEEDS MORE MUSCLE - HAS TO PUMP BLOOD AROUND WHOLE BODY, NOT JUST TO LUNGS
• SEMILUNAR, BICUSPID AND TRICUSPID VALVES PREVENT BACKFLOW OF BLOOD

ANIMAL AND PLANT GROWTH

• PLANTS - GROW CONTINUOUSLY - GROWTH IN HEIGHT MAINLY TO DO WITH CELL ELONGATION - CELL DIVISION HAPPENS IN TIPS OF ROOTS AND SHOOTS
• ANIMALS - GROW UNTIL THEY RRERACH A FINITE SIZE THEN STOP GROWING - GROWTH HAPPENS BY CELL DIVISION IN TIPS OF ROOTS AND SHOOTS

STEM CELLS

• DIFFERENCIATION - THE PROCESS IN WHICH CELL CHANGES TO BECOME SPECIALISED FOR ITS JOB
• ABILITY TO DIFFERENTIATE LOST AT EARLY STAGE IN HUMANS - PLANTS NEVER LOSE IT
• MOST CELLS IN BODY SPECIALISED FOR A PARTICULAR JOB
• STEM CELLS - UNDIFFERENTIATED CELLS - CAN DEVELOP INTO DIFFERENT TYPES OF CELLS TISSUES AND ORGANS DEPENDING ON INSTRCTIONS GIVEN
• FOUND IN EMBYOS - HAVE ABILITY TO TURN INTO ANY CELL, TISSUE OR ORGAN
• ADULTS HAVE STEM CELLS - ONLY FOUND IN BONE MARROW - AREN'T AS VERSITILE AS EMBRTO STEM CELLS - CAN ONLY TURN INTO CERTAIN CELLS

STEM CELL RESEARCH - BENEFITS

• BLOOD CANCER - CURED WITH BONE MARROW TRANSPLANTS - CONTAINS CERTAIN ADULT STEM CELLS - TURN INTO NEW BLOOD CELLS TO REPLACE OLD ONES
• EARLY HUMAN EMBRYOS - CONTAINS LOTS OF STEM CELLS - SCIENTISTS CAN EXTRACT THESE CELLS AND GROW THEM - WILL EVENTUALLY BE ABLE TO GROW TISSUES TO TREAT MEDICAL CONDITIONS

STEM CELL RESEARCH - ARGUMENTS FOR AND AGAINST

• FEEL THAT HUMAN EMBRYOS SHOULDN'T BE USED FOR EXPERIMENTS - EACH ONE POTENTIAL LIFE
• OTHERS THINK PATIENTS WHO ALREADY EXIST AND SUFFERING ARE MORE IMPORTANT THAN EMBRYOS
• EMBRYOS USED IN RESEARCH - ONES WHUCH HAVE BEEN DISCARDED IN FERTILITY CLINICS - WOULD HAVE BEEN THROWN AWAY ANYWAY
• CAMPAIGNERS FOR EMBRYO RIGHTS PROTEST THIS TOO
• NOW 'STOCKS' OF STEM CELLS - SCIENTISTS CAN USE THEM FOR RESEARCH
• SOME COUNTRIES E.G. USA WON'T FUND RESEARCH TO MAKE NEW STEM CELL STOCKS - UK ALLOWS IT UNDER STRICT GUIDELINES

METHODS OF MEASURING GROWTH

• LENGTH - MEASURING LENTH OR HEIGHT OF PLANT OR ANIMAL - EASY TO MEASURE - BUT DOESN'T TELL YOU ABOUT CHANGES IN WIDTH, DIAMETER, NUMBER OF BRANCHES ETC.
• WET MASS - WEIGHING PLANT OR ANIMAL - EASY TO MEASURE - BUT CHANGABLE - PLANT IS HEAVIER WHN IT'S RECENTLY RAINED, ANIMALS HEAVIER WHEN BLADDER FULL ETC.
• DRY MASS - DRYING OUT ORGANISM BEFORE WEIGHING IT - NOT AFFECTED BY AMOUNT OF WATER ORGANISM HAS HAD - BUT ORGANISMS HAVE TO BE KILLED BEFORE BEING WEIGHED

PHASES OF HUMAN GROWTH

• INFANCY - ROUGHLY FIRST TWO YEARS OF LIFE - RAPID GROWTH
• CHILDHOOD - PERIOD BETWEEN INFANCY AND PUBERTY - STEADY GROWTH
• ADOLESCENCE - BEGINS WITH PUBERTY - CONTINUES UNTIL BODY GROWTH AND DEVELOPMENT COMPLETE - RAPID GROWTH
• MATURITY/ADULTHOOD - PERIOD BETWEEN ADOLESCENCE AND OLD AGE - GROWTH STOPS
• OLD AGE - USUALLY CONSIDERED BETWEEN AGE OF 65 AND DEATH

MAIN PHASES OF RAPID GROWTH

• JUST AFTER BIRTH AND DURING ADOLESCENCE
• TYPICAL HUMAN GROWTH CURVE - STRETCHED S SHAPE - STEEPER CURVE - MORE RAPID GROWTH

GROWTH RATES OF DIFFERENT BODY PARTS

• BODY DOESN'T GROW EVENLY
• DIFFERENT PARTS OF BODY GROWS AT DIFFERENT RATES AT DIFFERENT TIMES
• E.G. IN EMBRYOS, BRAIN GROWS FASTEST - GIVES HUMANS BEST SURVIVAL ADVANTAGE - BEST TOOL HUMANS HAVE FOR FINDING FOOD, AVOIDING PREDETORS ETC.

SELECTIVE BREEDING - HUMANS ARTIFICIALLY SELECT PLANTS OR ANIMALS TO BREED TO HAVE THEIR GENES STAY IN THE POPULATION ACCORDING TO WHAT WE WANT FROM THEM

• ORGANISMS ARTIFICIALLY SELECTED TO DEVELOP FEATURES SUCH AS:
  • MAXIMUM YEILD OF MEAT, MILK, GRAIN ETC.
  • GOOD HEALTH AND DISEASE RESISTANCE
  • SPEED, ATTRACTIVENESS ETC.
• PRCESS OF SELECTIVE BREEDING INVOLVES:EXAMPLE - AGRICULTURE - IMPROVE YEILD - E.G. FARMERS BREED ANIMALS WITH BEST CHARACTERISTICS FOR PRODUCING MEAT TOGETHER FOR HIGHER MEAT YEILD
  • SELECT ONES FROM EXISTING STOCK WHICH HAVE BEST CHARACTERISTICS
  • BREED THEM WITH EACHOTHER
  • SELECT BEST OFFSPRING - BREED THEM TOGETHER
  • CONTINUE PROCESS OVER SEVERAL GENERATIONS

REDUCTION IN GENE POOL

• GENE POOL - NUMBER OF DIFFERENT ALELLES PRESENT IN POPULATION
• INBREEDING - FARMER BREEDS BEST ANIMALS - CLOSELY RELATED 
• HEALTH PROBLEMS - MORE CHANCE OF ORGANISM DEVELOPING GENETIC DISORDERS - LOTS OF GENETIC CONDITIONS RECESSIVE - NEED TWO ALLELES TO BE SAME TO HAVE AN EFFECT - RECESSIVE ALLELES MORE LIKELY TO BUILD UP IN POPULATION IF CLOSELY RELATED ANIMALS ARE BREEDED TOGETHER
• NEW DISEASE APPEARS - SERIOUS PROBLEM - NOT MUCH VARIATION IN POPULATION - STOCK CLOSELY RELATED - ONE OF THEM IS KILLED THEN OTHERS LIKELY TO BE KILLED

GENETIC ENGINEERING - MOVING GENES FROM ONE ORGANISM TO ANOTHER SO THAT IT PRODUCES USEFUL BIOLOGICAL PRODUCTS

• GENE RESPONSIBLE FOR PRODUCING DESIRABLE CHARACTERISTIC SELECTED 
• CUT FROM DNA USING ENZYMES AND ISOLATED
• USEFUL GENE INSERTED INTO DNA OF ANOTHER ORGANISM
• ORGANISM REPLICATES - LOADS OF SIMILAR ORGANISMS PRODUCTING USEFUL PRODUCT

EXAMPLES OF GENETIC ENGINEERING

• VITAMIN A - TAKE GENES FROM CARROTS THAT CONTROL BETA CAROTINE PRODUCTION - PUT THEM IN RICE - RICE EATEN THROUGHOUT WORLD - HUMANS CHANGE BETA CAROTINE INTO VITAMIN A
• INSULIN - GENE FOR HUMAN INSULIN PRODUCTION PUT INTO BACTERIA - CULTURED IN FERMENTER - HUMAN INSULIN EXTRACTED FROM MEDIUM AS THEY PRODUCE IT
• RESISTANCE TO HERBICIDES, FROST DAMAGE AND DISEASE - CUT OUT OF PLANTS THAT WE DON'T WANT TO GROW AND PUT INTO USEFUL ONES

ADVANTAGES AND RISKS OF GENETIC ENGINEERING

• ADVANTAGE - CAN PRODUCE ORGANISMS WITH NEW AND USEFUL FEATURES VERY QUICKLY
• RISK - INSERTED GENE MAY HAVE UNEXPECTED, HARMFUL EFFECTS - E.G. GENETICALLY ENGINEERED BACTERIA MAY MUTATE AND BECOME PATHOGENETIC - FOREIGN GENES MAY MAKE THEM MORE HARMFUL AND UNPREDICTABLE
• RISK - GENES MAY ESCAPE - E.G. WEEDS GAIN PESTICIDE RESISTANT GENES FROM USEFUL PLANT

ETHICAL ISSUES

• WRONG TO GENETICALLY ENGINEER ORGANISMS PURELY FOR HUMAN BENEFIT - PARTICULAR PROBLEM WITH GENETIC ENGINEERING OF ANIMALS, PARTICULARLY IF ANIMAL HARMED
• WON'T STOP AT PLANTS AND ANIMALS - RICH MAY BE ABLE TO PAY FOR BABY TO BE GENETICALLY ENGINEERED TO HAVE GOOD CHARACTERISTICS - THOSE WHO CAN'T AFFORD IT WILL BE 'GENETIC UNDERCLASS'
• EVOLUTIONARY CONSEQUENCES UNKNOWN - IRRESPONSIBLE IF WE DON'T KNOW THE IMPACT ON FUTURE GENERATIONS

GENE THERAPY - ALTERING A PERSONS GENES TO CURE GENETIC DISORDERS - TWO TYPES:

• CHANGING BODY CELLS - PARTICULARLY CELLS MOST AFFECTED BY DISORDER - E.G. CYSTIC FIBROSIS - LUNGS WOULD BE TARGETED - WOULDN'T AFFECT GAMETES - DISEASE COULD STILL BE INHERITED
• CHANGING GENES IN GAMETES - EVERY CELL IN BODY OF OFFSPRING AFFECTED - WON'T INHERIT DISEASE - CURRENTLY ILLEGAL

ETHICAL ISSUES OF GAMETE THERAPY

• UNEXPECTED CONSEQUENCES - CAUSE NEW SET OF PROBLEMS - HARMFUL GENES INHERITED BY OFFSPRING
• COULD LEAD TO CREATION OF 'DESIGNER BABIES' - PARENTS CHOOSE GENES THEY WANT CHILDREN TO HAVE

CLONES - GENETICALLY IDENTICAL ORGANISMS

CLONING OF ADULT ANIMAL - DONE BY TRANSFERRING THE NUCLEUS - NUCLEAR TRANSFER - E.G. DOLLY SHEEP

• NUCLEUS OF SHEEPS EGG CELL REMOVED - LEFT EGG WITHOUT ANY GENETIC INFORMATION
• ANOTHER NUCLEUS INSERTED IN IT'S PLACE - DIPLOID NUCLEUS FROM UDDER CELL OF SHEEP BEING CLONED - HAD ALL OTHER SHEEPS GENETIC INFORMATION
• CELL GIVEN ELECTRIC SHOCK - STARTED DIVIDING MY MITOSIS
• DIVIDING CELL )NOW AN EMBREO) PLANTED INTO UTERUS OF SURROGATE MOTHER SHEEP TO DEVLOP UNTIL READY TO BE BORN
• RESULT - DOLLY - CLONED SHEEP FROM WHICH THE UDDER CELL CAME

CLONING HUMANS - ETHICAL ISSUES

• LOTS OF SURROGATE PREGNANCIES - HIGH RATES OF MISCARRIAGE AND STILLBIRTH
• CLONES OF OTHER ANIMALS HAVE BEEN UNHEALTHY - OFTEN DIE PREMATURELY
• CLONE MAY BE PSYCOLOGICALLY DAMAGED TO KNOW THAT IT'S JUST A CLONE OF ANOTHER HUMAN

BENEFITS OF CLONING

• ALLOWS PRODUCTION OF ANIMALS WITH DESIRABLE CHARACTERISTICSHUMAN EMBREOS PRODUCED BY CLONING ADULT BODY CELLS - EMBREOS USED TO SUPPLY STEM CELLS FOR STEM CELL THERAPY - EXACTLY THE SAME GENETIC INFORMATION AS PATIENT - REDUCED RISK OF REJECTION
  • ANIMALS WHICH PRODUCE MEDICINES IN THEIR MILK DEVELOPED BY GENETIC ENGINEERING AND CLONED - USEFUL HUMAN GENES TRANSFERRED TO SHEEP AND COWS AND PUT INTO HUMANS WITHOUT USEFUL GENE E.G. BLOOD CLOTTING AGENT PUT INTO PEOPLE WITH HAEMOPHILIA
  • ANIMALS WITH ORGANS SUITABLE FOR TRANSPLANTATION CLONED - CONSTANT SUPPLY OF ORGANS FOR TRANSPLANT - SOLVE PROBLEM OF LIMITED SUPPLY (ALTHOUGH THERE ARE ISSUES E.G. VIRUSES PASSED FROM ANIMALS TO HUMANS)

RISKS OF CLONING

• CLONES NOT AS HEALTHY AS NORMAL ANIMALS
• NEW SCIENCE - MAY HAVE CONSEQUENCES WE'RE NOT YET AWARE OF

COMMERCIAL CLONING OF PLANTS - EASIER THAN CLONING ANIMALS

• PLANT WANTED IS CHOSEN BASED ON CHARACTERISTICS
• REMOVE SEVERAL SMALL PIECES OF TISSUE FROM PARENT PLANT - BEST RESULTS IF TISSUE TAKEN FROM FAST GROWING SHOOTS OR TIPS
• GROW TISSUE IN GROWTH MEDIUM CONTAINING NUTRIENTS AND GROWTH HORMONES - DONE UNDER ANTISEPTIC CONDITIONS TO PREVENT MICROBE HARMING PLANT
• TISSUES PRODUCE SHOOTS AND ROOTS - MOVED TO POTTING COMPOST TO CARRY ON GROWING

COMMERCIAL USE OF CLONED PLANTS - PROS AND CONS

• PRO - CAN BE FAIRLY SURE OF CHARACTERISTICS OF PLANT - GENETICALLY IDENTICAL TO PARENTS - DON'T WASTE TIME OR MONEY GROWING BAD PLANTS
  • POSSIBLE TO MASS PRODUCE PLANTS THAT ARE HARD TO GROW FROM SEEDS
• CON - SUFFER FROM DISEASE DUE TO CHANGE IN ENVIRONMENT - ALL PLANTS WILL SUFFER - SAME GENES
  • LACK OF GENETIC VARIATION