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a number of different presynaptic neurones collectively release enough
neurotransmitters to exceed the threshold value of the postsynaptic neurone, triggering
a new action potential.
spatial summation
acetyl groups added to histones, so DNA is less tightly wound round it, making it easier
for RNA polymerase and transcriptional factors to bind, so transcription can occur.
, acetylation of DNA
because males only have one X chromosome, and so if there is a recessive allele there,
then there will be no dominant allele on Y chromosome to "hide" it.
why are sex linked diseases more common in males than females?
1. stimulus- heat
2. receptor- heat receptors to sensory neurone
3. sensory neurone- impulse to spinal cord
4. relay neurone- to motor neurone
5. motor neurone- spinal cord to muscle
6. effector- muscle in arm contracts
7. response- pulling hand away from heat
describe the components of a reflex arc and give an example.
contract more slowly and provide less powerful contractions but over a longer period.
adapted for aerobic respiration to avoid lactic acid build up.
adapted for endurance work.
has lots of myoglobin, rich bloody supply and many mitochondria.
, describe slow twitch fibres
nitrogen rich soils favour the growth of grasses etc., which can outcompete other
species, which die as a result.
why does using nitrogen containing fertilisers result in reduced species
diversity?
1. extract DNA. quantity of DNA may be increased by PCR.
2. restriction endonucleases cut DNA into fragments.
3. gel electrophresis. dna put onto agar gel, voltage is applied across it. smaller
fragments mover further than larger fragments.
4. DNA hybridisation- DNA probes have complimentary base sequences to non-coding
DNA, and so bind under specific conditions.
5. X-ray film is exposed to radiation from probes. this film is put over a nylon membrane.
a series of bars is shown which corresponds to the movement of the fragments.
explain the steps of genetic fingerprinting.
a form of response whereby an organism changes the speed in which it moves and
changes direction. this occurs when an organism reaches an area of unfavourable stimuli,
, so that it may return to a favourable environment.
what is a kinesis?
1.osmoreceptors in hypothalamus detect fall in water potential as they begin to shrink,
causing hypothalamus to produce ADH.
2. ADH goes to posterior pituitary gland, where it is secreted into capillaries.
3. ADH goes from blood to kidneys, where it binds to receptors on the cells of of distil
convoluted tubule and collecting duct.
4. this activates phosphorylase enzyme.
5. this causes vesicles, which contain water channel proteins, to fuse with cell surface
membrane. hence, making it more permeable to water.
6. also increases permeability of collecting duct to urea so it passes out and lowers
water potential, so more water can pass out by osmosis.
describe and explain the role of hormones in osmoregulation.
p2 + 2pq + q2
p2 = homozygous dominant
q2 = homozygous recessive
2pq = heterozygous
In any hardy-weinberg problem, start with homozygous recessive individuals.
a number of different presynaptic neurones collectively release enough
neurotransmitters to exceed the threshold value of the postsynaptic neurone, triggering
a new action potential.
spatial summation
acetyl groups added to histones, so DNA is less tightly wound round it, making it easier
for RNA polymerase and transcriptional factors to bind, so transcription can occur.
, acetylation of DNA
because males only have one X chromosome, and so if there is a recessive allele there,
then there will be no dominant allele on Y chromosome to "hide" it.
why are sex linked diseases more common in males than females?
1. stimulus- heat
2. receptor- heat receptors to sensory neurone
3. sensory neurone- impulse to spinal cord
4. relay neurone- to motor neurone
5. motor neurone- spinal cord to muscle
6. effector- muscle in arm contracts
7. response- pulling hand away from heat
describe the components of a reflex arc and give an example.
contract more slowly and provide less powerful contractions but over a longer period.
adapted for aerobic respiration to avoid lactic acid build up.
adapted for endurance work.
has lots of myoglobin, rich bloody supply and many mitochondria.
, describe slow twitch fibres
nitrogen rich soils favour the growth of grasses etc., which can outcompete other
species, which die as a result.
why does using nitrogen containing fertilisers result in reduced species
diversity?
1. extract DNA. quantity of DNA may be increased by PCR.
2. restriction endonucleases cut DNA into fragments.
3. gel electrophresis. dna put onto agar gel, voltage is applied across it. smaller
fragments mover further than larger fragments.
4. DNA hybridisation- DNA probes have complimentary base sequences to non-coding
DNA, and so bind under specific conditions.
5. X-ray film is exposed to radiation from probes. this film is put over a nylon membrane.
a series of bars is shown which corresponds to the movement of the fragments.
explain the steps of genetic fingerprinting.
a form of response whereby an organism changes the speed in which it moves and
changes direction. this occurs when an organism reaches an area of unfavourable stimuli,
, so that it may return to a favourable environment.
what is a kinesis?
1.osmoreceptors in hypothalamus detect fall in water potential as they begin to shrink,
causing hypothalamus to produce ADH.
2. ADH goes to posterior pituitary gland, where it is secreted into capillaries.
3. ADH goes from blood to kidneys, where it binds to receptors on the cells of of distil
convoluted tubule and collecting duct.
4. this activates phosphorylase enzyme.
5. this causes vesicles, which contain water channel proteins, to fuse with cell surface
membrane. hence, making it more permeable to water.
6. also increases permeability of collecting duct to urea so it passes out and lowers
water potential, so more water can pass out by osmosis.
describe and explain the role of hormones in osmoregulation.
p2 + 2pq + q2
p2 = homozygous dominant
q2 = homozygous recessive
2pq = heterozygous
In any hardy-weinberg problem, start with homozygous recessive individuals.
