Biology unit 5 topic 8

How is seeing possible?

Because the cells of the nervous system are able to conduct nerve impulses and pass them to one another

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What is dependent on nerve impulses?

All our senses, emotions, memories and thoughts

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What is a neurone?

A single specialised cell that transmits nerve impulses

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What is a nerve?

A complex structure containing a bundle of the axons of many neurones, surrounded by a protective covering (several axons held together)

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What is the nervous system made up of?

Central nervous system (CNS) and peripheral nervous system (PNS)

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What does the central nervous system consist of?

Brain and spinal chord

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What does the peripheral nervous system consist of?

sensory nerves (carrying sensory information from the receptors to the CNS) and motor nerves (carrying motor commands from CNS to effectors)

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What is the peripheral nervous system subdivided into?

Autonomic nervous system and somatic nervous system

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What is the role of the autonomic nervous system?

Involuntary-stimulates smooth muscle, cardiac muscle and glands (involuntarily regulates internal body functions)

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What is the role of the somatic nervous system?

Voluntary- stimulates skeletal muscle (voluntarily responds to external stimuli)

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What is the autonomic nervous system subdivided into?

Sympathetic nervous system and parasympathetic nervous system

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What is the role of the sympathetic nervous system?

Prepares body for 'fight or flight response' (intense physical activity) e.g. speeds up heart rate

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What is the role of the parasympathetic nervous system?

prepares body for 'rest and digest' (relaxes the body and inhibits of slows down many high energy functions)

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What happens when the sympathetic nervous system is stimulated?

1.Heart rate increases(more O2+nutrients to brain+muscles) 2.Liver releases glucose more energy for muscles) 3.Bronchioles dilate(more oxygenation) 4.Pupils dilate 5.Adrenal glands secrete epinephrine and norepinephrine(sustain response) 6.no digest

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What are the adrenal glands?

A pair of hormone producing glands located on top of the kidneys that respond to stress

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What does the cell body of a neurone contain?

The nucleus and cell organelles within the cytoplasm

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What are the two types of thin extensions from the cell body?

Dendrites and the axon

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What is the role of an axon?

Transmits impulses away from the cell body

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What is the role of dendrites?

Conducts impulses towards the cell body

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What is produced by Schwann cell around the axon

Layer of lipid

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Describe the structure of a motor neurone

Cell body on one side of the axon and terminal branches on the other.

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Describe the structure of a sensory neurone

Cell body coming up out the centre of the axon with dendrites on either side of the axon

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Describe the structure of a relay neurone

Cell body in the centre of the axon with dendrites on either side of the axon

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What are the tree main types of neurone?

Motor, sensory and relay

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What is the role of motor neurones?

Conducts impulses from the CNS to effectors (muscles or glands)

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Where is the cell body of a motor neurone always found?

Within the CNS

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What is the role of sensory neurones?

Carry impulses from sensory cells to the CNS

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What is the role of relay neurones?

Carry impulses from one part of the CNS to another

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What is mylin sheath?

A fatty insulating layer around the axon that is made up of Schwann cells and affects how fast nerve impulses pass along the axon

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What happens when the body is exposed to a stimulus? (1)

Receptors detect the stimulus and generate a nerve impulse

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What do sensory neurones do to a nerve impulse? (2)

Conduct the nerve impulse to the CNS along a sensory pathwway

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How do sensory neurones enter the spinal chord? (3)

Through the dorsal route

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What does the sensory neurone form a synapse with? (4)

A relay neurone

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What does a relay neurone form a synapse with? (5)

A motor neurone that leaves the spinal chord through the ventral route

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What does the motor neurone do to the nerve impulse? (6)

Carries impulses to an effector which produces a response

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What are reflex arcs?

Nerve pathways through the nervous system that are responsible for our reflexes (rapid, involuntary response to stimuli)

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What does the iris do?

Controls the size of the pupil

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What does the iris contain?

A pair of antagonistic muscles-radial and circular muscles

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What are the radial and circular muscles controlled by?

Autonomic nervous system. Radial muscles are controlled by a sympathetic reflex whilst circular muscles are controlled by a parasympathetic reflex

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What is the advantage of reflex pathways?

They produce rapid responses; important for protection and survival

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What happens when high levels of light hit the photoreceptors in the retina?

Nerve impulses pass along the optic nerve to different sites in the CNS (group of coordinating cells).Impulses from cells sent along parasympathetic motor neurone to circular muscles causing them to contract-radial relax.Reducing light entering eye

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What happens to pupils in high levels of light?

Contract-to reduce the amount of light entering the eye

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What happens to pupils in low levels of light?

Dilate-to increase the amount of light entering the eye

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What is the purpose of the pupil reflex?

To prevent damage to the retina from high-intensity light and in dim light it ensures the maximum light reaches the retina

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The pupil reflex response to increased light is very rapid. Why does this need to be the case?

To protect the eye from sudden flashes of bright light

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How many synapses are there in the pupil reflex pathway?

Three per eye

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What is the resting potential value?

-70mV

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How is the uneven distribution of ions across the cell surface membrane achieved?

By the action of sodium-potassium pumps. Carry Na+ out of cell and K+ into cell.Pump acts against concentration gradient of ions.Energy supplied by the hydrolysis of ATP.Organic anions large,stay in cell so Cl- moves out to balance charge across memb

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Where are sodium-potassium pumps found?

In the cell surface membrane of the axon

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Why is the axon resting potential -70mV

1.Na+/K+ pump creates conc gradient 2.K+ diffuse out of cell down concentration gradient, outside more + inside more - 3.Electrical gradient pulls K+ back into cell 4.At -70mV the two gradients counteract each other and there is no net movement of K+

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Why is the cell surface membrane more permeable to potassium ions than sodium ions?

Have more K+ channels than Na+ channels

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What is the name of the gap between the mylin sheeth?

Node of Ranvier

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What prevents depolarisation from spreading backwards along the axon?

Sodium channel inactivation

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What happens if an electrical current above a threshold level is applied to the membrane?

Causes a massive change in the potential difference. The potential difference across the membrane is reversed, making the inside of the axon positive and the outside negative-this is known as depolarisation

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What is the potential difference value during depolarisation?

+40mV

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Why is it important that the membrane of nerve is returned to the resting potential as soon as possible?

In order for more impulses to be conducted

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What is repolarisation?

The returning to a potential difference of -70mV in the membrane

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What is action potential?

The large change in the voltage across the membrane

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What is depolarisation?

Reversing the potential difference across the membrane, making the inside of the axon positive and the outside negative

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What are the three stages in the generation of an action potential?

1.Depolarisation 2. Repolarisation 3.Restoring the action potential

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What happens during depolarisation

Neurone is stimulated causing voltage gated sodium channels to open allowing the flow of Na+ into the axon. The opening of gates increases depolarisation causing more gates to open.Inside of the axon becomes more positive +40mVW

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What is positive feedback?

When one change encourages another change

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What happens during repolarisation?

Voltage gated sodium channels close and voltage gated potassium channels open.Potassium ions move out of the axon down the electrochemical gradient.As potassium flows out inside becomes more negative FR4

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What happens during the restoration of resting potential?

Membrane highly permeable to K+ and more K+ moves out than at resting potential making it more negative than normal.This is known as hyperpolarisation.Resting potential re-establish by closing voltage dependent K+ gates and K+ diffuse into axon

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Will it be possible for an action potential to be triggered in a dead axon?Give a reason for your answer

No(unless ATP was added); the polarisation of the membrane is maintained by the concentration gradients achieved by energy requiring Na+/K+ pumps; membrane integrity is lost in a dead axon

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How does the refractory period ensure that an action potential will not be propagated back the way it came from?

A new action potential will only be generated at the leading edge of the previous one because the membrane behind it will be recovering; the membrane has to be repolarised and return to resting potential before another action potential can be genera

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What is refractory period?

A new action potential cannot be generated in the same section of membrane for about 5ms

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What does the size of the stimulus affect?

The frequency of impulses and the number of neurones in a nerve that are conducting impulses

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What is the speed of nervous conduction determined by?

The diameter of the axon and the presence of a mylin sheeth.The wider the diameter, the faster the impulse travels

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Describe saltatory conduction

Mylin sheath acts as an electrical insulator along axon preventing flow of ions across membrane.Nodes of Ranvier are only place where depolarisation occurs.Impulse jumps from nodes.Faster wave of depolarisation

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What is a synapse?

Where two neurones meet

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What is synaptic cleft

The small gap between two neurones

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Where can synaptic vesicles be found and what do they contain?

Found in the cytoplasm at the end of the presynaptic neurone and contain a chemical called neurotransmitter

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How does a synapse transmit an impulse?

1.Pre membrane depolarises 2.Ca2+ channels open and Ca2+ enters neurone 3.Ca2+ causes exocytosis of vesicles containing neuro 4.Neuro released into synaptic cleft 5.Neuro binds with receptors on post-s,cation channels open.Na+ flows in 6.Post depolar

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What is embedded in the postsynaptic membrane?

Specific receptor proteins that have a binding site complimentary to part of the neurotransmitter molecule

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What happens when the neurotransmitter binds to receptors on the postsynaptic membrane?

Changes the shape of the receptor protein, opening cation channels and making the membrane more permeable to Na+ which causes depolarisation

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What enzyme is used to break down acetycholine so that it cannot bind to receptors?

Acetylecholinesterase

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What are the two roles of synapses?

Control of nerve pathways (allowing flexibility of response) and integration of information from different neurones allowing a coordinated respone

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What are the two main factors affect the likelihood that the postsynaptic membrane will depolarise?

1.The type of synapse 2.The number of impulses recieved

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What are the two different types of synapses in a postsynaptic cell?

Inhibitory and excitatory synapses

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What is the role of an excitatory synapse?

Helps stimulate an action potential in the postsynaptic membrane as it makes it more permeable to Na+ ions

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What is the role of an inhibitory synapse?

Reduces the likelihood that the postsynaptic membrane will depolarise by opening channels for chloride ions and potassium ions.This makes the inside of the membrane more negative -90mV so depolarisation is less likely to occ

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Suggest how an inhibitory synapse might work to make it less likely that the postsynaptic membrane will depolarise

Ion channels open in the postsynaptic membrane; ions move through the channels increasing polarisation of the membrane; more excitatory synapses would be required to depolarise the membrane

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What is summation?

The fact that each impulse adds to the effect of others

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What are the two different types of summation?

Spatial summation and temporal summation

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What is spatial summation?

When the impulses come from different synapses, usually from different neurones.The number of different sensory neurons stimulated can be reflected in the control of the response

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What is temporal summation?

Several impulses arrive at a synapse having travelled along a single neurone.Their combined release of neurotransmitter generates an action potential in the postsynaptic membrane

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Describe nervous control

Electrical transmission by nerve impulses and chemical transmission at synapses, it is fast acting and is usually associated with short-term changes.Action potentials carried by neurones with connections to specific cells.Response often local

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Describe hormonal control

Chemical transmission through blood, slower acting and can control long-term changes .Blood carries the hormone to all cells but only target cells are able to respond.Response is widespread

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What do animals use nervous and hormonal control for?

To coordinate activity in the body

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What do plants use chemicals for?

Lack a nervous system so use chemicals to coordinate growth, development and response to the enviroment

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What are plant growth substances?

Chemicals produced in the plant in very low concentrations and transported to where they cause a response

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What is the role of auxin?

To stimulate growth by cell elongation

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Explain why model produced to explain growth curvature resulting from unequal distribution of auxin is widely criticised?

1.Small sample sizes 2.Difficulty measuring very small concentrations involved

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Where are auxins synthesised?

In actively growing plant tissues (meristems) such as shoot tips, developing leaves,seeds and fruits

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What happens when auxin binds to receptors on the plasma membranes in the zone of shoot elongation?

Auxin produces a second signal messenger molecule that brings about changes in gene expression

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What does transcription of genes coding for enzymes result in?

Metabolic changes

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Explain how auxin causes acidification of the cell wall and what effect this has

By indirectly stimulating the activity of proton pumps that move H+ out of the cytoplasm.Low pH effects enzyme in cell wall that causes bonds between cellulose myofibrils to break allowing cell wall to expand

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What happens when auxin causes the cell wall to expand?

The increased potential difference across the membrane enhances the uptake of ions into the cell.This in turn causes uptake of water by osmosis, resulting in cell elongation

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What are stimuli detected by?

Receptor cells that send electrical impulses to the CNS

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What do sense organs do?

Protect receptor cells and improve their efficiency; structures within the sense organ ensure that the receptor cells are able to receive the appropriate stimulus

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What is the role of the lens?

Focuses light on the retina

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What is the role of the cornea?

Bends light in order for it to focus on the retina

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What is the role of the conjunctiva?

Protects the cornea

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What is the role of the ciliary muscle?

Alters the thickness of the lens for focusing

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What is the role of the choroid?

Is a black layer that prevents internal reflection of light

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What is the vitreous humour?

transparent jelly in the eye

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What is the role of the retina?

Contains light-sensitive cells-where photoreceptors are located

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What is the fovea?

It is the most sensitive part of the retina located within the macula (an oval yellowish area surrounding the fovea near the centre of the retina)

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What is the blind spot?

Area where the optic nerve leaves the eye that contains no light-sensitive cells

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What is the sclera?

Protective layer in the eye

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What is the role of the iris?

Controls the amount of light entering the eye

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What is the name of the two photoreceptor cells found in the retina?

Rods and cones

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What is the role of cones?

Allow colour vision in bright light

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What is the role of rods?

Give black and white vision in both dim lights and bright lights

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What are there more of rods or cones?

Rods

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What three layers of cell are arranged to make up the retina?

Rods and cones synapse with bipolar neurone cells, which in turn synapse with ganglion neurones, whose axons together make up the optic nerve

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What so the photochemical pigments in rods and cones doe?

Absorb light which results in a chemical change

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What is the name of the photochemical pigment in rods?

Rhodopsin (purplish pigment)

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What do the inner and outer segment of the rod cell contain?

Many flattened vesicles

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Where are rhodopsin molecules found?

In the membrane of the flattened vesicles found in the inner and outer segment of a rod cellg

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What happens to a rod cell in the dark?

Na+ flows into outer segment through non-specific cation channels.Na+moves down conc. gradient into inner segment where pumps pump them out of cell.Influx of Na+ produces depolar.Triggering release of neurot(glutamate).Binds to bipolar stops depolar

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What happens when light falls on a rhodopsin molecule?

Causes it to break down into retinal and opsin

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What does opsin do?

Activates a series of membrane bound reactions ending in hydrolysis of molecule attached to cation channel in outer segment.This results in cation channels closing

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What happens in rods when the cation channels close?

Influx of Na+ into rod decreases,while inner segment continues to pump Na+ out.This makes inside more negative(hyperpolarised).Release of glutamate stops.

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What happens when the release of glutamate stops in a rod cell?

Lack in glutamate results in the depolarisation of the bipolar cell with which the rod synapses.The neurones that make up the optic nerve are also depolarised and respond by producing an action potential

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By what form of transport will sodium ions be pumped out of the rod cell?

Active transport

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What is a non-specific cation channel?

One that lets any positive ions through such as Na+ and Ca2+

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Why does the rod cell membrane become hyperpolarised in the light?

Sodium ions are being actively transported out and their re-entry through ion channels is prevented; increasing the potential difference across the membrane

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What is essential once rhodopsin has been broken down?

That it is rapidly converted back to its original form so that subsequent stimuli can be percieved

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What is dark adaptation?

The reforming of rhodopsin

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Why are responses in plants slower than in animals?

All messages in plants are chemical

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What is a phytochrome?

A photoreceptor that absorbs red and far-red light

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What does a phytochrome molecule consist of?

A protein component bonded to a non-protein light-absorbing pigment molecule

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What are the two forms that the non-protein component in a phytochrome exist in?

Pr:phytochrome red;absorbs red light ---> Pfr:phytochrome far-red; absorbs far-red light (these are photoreversible)

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What form of the non-protein component of phytochromes is synthesised by plants?

Pr

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What causes Pr to be converted into Pfr?

Absorption of red light

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What causes Pfr to be converted back into Pr?

Absorption of far-red light

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What occurs to Pr and Pfr in sunlight?why?

Pr is converted into Pfr as more red light is absorbed than far-red light, so Pfr accumulates in the light

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What occurs to Pfr and Pr in the dark?

Pfr is slowly converted back into Pr

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What is regulated by phytochromes?

Seed germination, stem elongation, leaf expansion, chlorophyll formation and flowering

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Why do tiny seeds e.g. lettuce require light to germinate?

They have thin seed coats and few food reserves, and only germinate in optimum conditions

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How do tiny seeds respond to red and far red-light in terms of germination?

Flash of red light will trigger germination whilst if followed by flash of far-red light then germination is inhibited.If a flash of red light occurs again then germination is promoted again.Effects of red light and far-red light are reversible

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Suggest which isomer of phytochrome, Pr or Pfr, needs to be present to stimulate germination

Pfr

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Describe the mechanism that prevents lettuce seeds from germinating in the dark

In the dark no red light is absorbed so no Pfr is formed that would stimulate germination; any Pfr present is converted back to Pr which inhibits germination

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What is photoperiod?

Environmental cue that determines time of flowering

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What is a long-day plant?

A plant that only flowers when day length exceeds a critical value.They flower when the period of uninterrupted darkness is less than 12h;need Pfr to stimulate flowering

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Explain why a long-day plant can successfully flower in the summer

Long days have a short period of uninterrupted darkness;this is not long enough to convert all the Pfr back into Pr.The Pfr stimulates flowering

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What is a short-day plant?

A flower that tends to flower when the period of uninterrupted darkness is more than 12h.They need long hours of darkness to convert the Pfr back to Pr.Pfr inhibits flowering in these plants

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What is greening?

The changes made in both the form and biochemistry of a shoot once it has broken through the soil

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What is the role of phytochromes?

Promote the development of primary leaves, leaf unrolling and the production of pigments. They can also inhibit certain processes such as elongation of internodes

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How do phytochromes switch processes on or off?

Phytochromes bind to protein or disrupt binding of protein complex.Signal proteins act as transcr factors or activate transcr factors that bind to DNA to allow transcr of light-regulated genes.Transc & transl results in plants response to light

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What do phototropins determine?

Phototropic responses

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What are phototropins?

blue-light receptors controlling a range of responses that serve to optimize the photosynthetic efficiency of plants

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What is phototropism?

Growth of an organism which responds to a light stimulus

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What is the stimulus for shoot growth when it is more than a short distance under the soil surface?

Gravity.Response ensures that developing shoots reach the light while roots grow in the soil

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What is the cortex made up of?

Nerve cell bodies, synapses and dendrites

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What is the outer layer of the brain known as?

Grey matter

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What is each cerebral hemisphere composed of?

Frontal lobe, parietal lobe, occipital lobe and temporal lobe

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What is the corpus callosum

Broad band of white matter (nerve axons) that connects the two cerebral hemispheres

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What is the role of the frontal lobe?

Involved in decision making, reasoning, planning and conciousness of emotions

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What does the frontal lobe include?

Primary motor cortex which has neurones that connect directly to the spinal cord and brain stem and from there to the muscles.Sends info to body via motor neurones to carry out movements

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What is the role of the parietal lobe?

Involved in orientation, movement, sensation, calculation and some types of recognition and memory

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What us the role of the occipital lobe?

Processes information from the eyes e.g. vision, colour, shape recognition and perspective

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What is the role of the temporal lobe?

Processes auditory information e.g. hearing, sound recognition and speech. Also involved in memory

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Why may a blow to the back of the head result in you seeing stars?

The occipital lobe is at the back of the cortex and is involved in vision processing

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What is the role of the thalamus?

It is responsible for routing all the incoming sensory information to the correct part of the brain, via the axons of the white matter

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What is the role of the hypothalamus?

Contains a thermoregulatory centre which regulates the core body temperature.Also contains centres that control sleep, thirst and hunger as well as acting as an endocrine gland

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What is an endocrine gland?

A gland that secretes hormones straight into the bloodstream rather than through a duct

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What is the role of the hippocampus?

Is involved in laying down long-term memory

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What is the basal ganglia?

A collection of neurones that lie deep within each hemisphere and are responsible for coordinating movement

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What is the role of the cerebellum?

Responsible for balance and coordination of movement as well as ensuring the motor programme being used is the correct one

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What is the role of the midbrain?

Relays information to the cerebral hemispheres, including auditory information to the temporal lobe and visual information to the occipital lobe

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What is the role of the medulla oblongata

Regulates the body processes that we don't consciously control

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What is neural plasticity?

The potential of neurones to change in structure and function

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Describe how CTs work

Thousands of narrow-beam X-rays rotated around patient to pass through tissue at different angles.Strength of beam varies according to the density of the tissue in its path.The Xrays are detected and used to produce an image of a thin slice of brain

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What are the advantages of CTs?

Can look at soft tissue as it uses narrow-beam X-rays rather than broad-beam X-rays.Looks at structures in the brain and are used to detect brain disease and monitor the tissue in the brain over the course of an illness. Can be used frequently

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What are the disadvantages of CTs?

Only give 'frozen moment' pictures and have limited resolution so small structures in the brain cannot be distinguished

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Describe what MRIs do

Uses magnetic field and radio waves to detect soft tissue.Nuclei of atoms line up with direction of magnetic field. H atoms in H2O monitored as there is a high H2O content in tissues

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Describe how MRIs work

Two magnetic fields are superimposed this causes the direction and frequency of spin of nuclei to change taking energy from radiowaves to do so.When r.w turned off nuclei return to original alignment and release energy absorbed.Energy detected-image

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What are the advantages of MRIs?

Produces finely detailed 3D images of brain structures as a result of its good resolution

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What are fMRIs?

Tool that provides information about the brain in action by following the uptake of oxygen in active brain areas

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How do fMRIs work?

Deoxyhaeomoglobin absorbs radio wave signal whereas oxyhaemoglobin doesn't.Increase neural activity->more oxygen needed->more blood flow->increase in oxyhaemoglobin so less signal absorbed->Areas light up

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Describe what parts of the brain are involved in seeing and interpreting what we see

Axons of ganglion cells(make up optic nerve) go out of eye and go to several areas of brain including thalamus.Impulses sent along neurones to primary visual cortex-info processed further.Before reaching thalamus neurones go to midbrain-turn to stimu

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What factors cause the large postnatal increase in size?

1.Elongation of axons 2.Myelination 3.Development of synapses

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What happens when axons of the neurons from the retina grow to the thalamus?

They form synapses with neurones in the thalamus in a very ordered arrangement.Axons from these thalamus neurones grow towards the visual cortex in the occipital lobe

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What shows that the visual cortex is made of columns of cells?

Staining techniques and studies using electrical stimulation

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What is critical window?

A period of time during postnatal development when the nervous system must obtain specific experiences to develop properly.

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Describe the Hubel and Wiesel experiment with monkeys

Deprived newborn monkeys of light stimulus in 1 eye(monocular deprivation).After 6 months eye exposed to light.Monkey blind in light-deprived eye.Retinal cells in light deprived eye did respond to light stimuli,cells in visual cortex didn't.

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Describe the Hubel and Wiesel experiment with kittens

1.Deprivation under 3 weeks had no effect 2.Deprivation after 3 months had no effect 3.Deprivation at 4 weeks had a major effect

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How do we recognise objects that are close to us?

Cells in the visual cortex obtain information from both eyes at once this is done by stereoscopic vision which allows the relative position of objects to be percieved

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What is stereoscopic vision?

When the visual field is seen from two different angles and the cells in the visual cortex let us compare the view from one eye with that from the other

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Why might a child who has had an eye patch during visual development never develop stereoscopic vision?

Synapses from optic nerve axon to visual cortex are weakened or eliminated;binocular cells in visual cortex can only receive sensory info from one eye;so will not have 2 visions to compare; making stereoscopic vision difficult or impossible

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State the ethics for the use of animals in studies

1.Only done when necessary and scientists follow strict rules 2.Humans have a greater right to life than animals as they have more complex brains 3.Animals similar to humans so many medical break through

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State the ethics agains the use of animals in studies

1.Drugs affect animals in a different way 2.Can cause pain and distress to animals 3.Have right to life 4.Alternatives to using animals in research

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How do we recognise distant objects?

Visual cues and past experiences are used when interpreting the images.Lines converge in the distance giving the impression of distance.As well as that overlaps of objects and changes of colour also help in judging depth1

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State the two ways that memories can be created

By altering the pattern of connections and the strength of synapses

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What is habituation?

A type of learning which allows animals to ignore unimportant stimuli so that limited sensory, attention and memory resources can be concentrated on more threatening or rewarding stimuli

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Describe how an animal becomes habituated

With repeated stimulation Ca2+ channels become less reponsive so less Ca2+ crosses presynaptic membrane.Less neurotransmitter released.Less depolarisation of postsynaptic membrane so no action potential triggered in motor neurone

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Describe Kandels experiment on habituation

Stimulated sea slug's siphon repeatedly with jet of water.Response gradually faded until gill no longer withdrew.Neurones involved in reflex identified.Amount of neurotransmitter crossing synapse between sensory and motor neurones decreased with habi

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Describe what long-term memory storage involves

Increase in the number of synaptic connections.Repeated use of a synapse leads to the creation of additional synapses between the neurones

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Describe the cause of parkinson's disease

Dopamine-secreting neurones in the basal ganglia die. These neurones normally release dopamine in the motor cortex. Parkinson's patients motor cortexes receive little dopamine so there is a loss of control of muscular movement

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Describe how drugs such as selegiline work as a treatment for Parkinson's disease

Slow down the loss of dopamine by inhibiting the enzyme monoamine oxidase which is responsible for breaking down dopamine

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Describe how dopamine agonist work as a treatment for Parkinson's disease

Are drugs that activate the dopamine receptors directly by acting like dopamine and binding to dopamine receptors at synapses to trigger action potentials

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Describe how gene therapy is used as a treatment for Parkinson's disease

Genes for proteins that increase dopamine production and promote growth and survival of nerve cells are inserted into the brain

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Suggest why non-peptide compounds that can introduce proteins that aid survival of neurones are being developed

Non-peptide compounds will not be digested as they pass through the gut so can be given to the patient orally

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What is the role of serotonin?

A neurotransmitter that plays an important role in determining a person's mood

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What is a possible cause of depression?

A lack of serotonin

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What is the 5-HTT gene know to do?

Influence our susceptibility to depression, it codes for a transporter a transporter protein that controls serotonin reuptake into neurones.People with the short version of this gene are more likely to develop depression after stressful event

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In depression,alleles at many loci are thought to be involved in the inheritance of the condition.State the name of this pattern of inheritance

Polygenic inheritance

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What happens when a person is depressed?

Fewer nerve impulses are transmitted around the brain,which may be related to low levels of neurotransmitter being produced.Molecules needed for serotonin synthesis are present in low levels by there is more serotonin-binding sites.

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What do SRRIs do and how are they used to treat symptoms of depression?

SRRIs block the reuptake of serotonin from synaptic clefts. This maintains a higher level of serotonin and so increases the rate of nerve impulses in serotonin pathways

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What effects does ecstasy have?

Affects thinking, mood and memory. Can cause anxiety and altered perception.The most desirable effect of ecstasy is its ability to provide feelings of emotional warmth and empathy

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How does ecstasy affect the synapses?

Increases concentration of serotonin in the synaptic cleft.Does this by binding to molecules on the presynaptic membrane responsible for reuptake of serotonin.Prevents removal from synaptic cleft.They can also cause these molecules to work in reverse

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What are some of the side effects of ecstasy?

Clouded thinking, agitation, disturbed behaviour , sweating and increased heart rate

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What is a drug target?

A specific molecule that a drug interacts with to bring about its change

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What are some of the ethical problems caused by the human genome project?

1.Insurance companies and employers can discriminate 2.Confidentiality

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What is genetic modification?

The artificial introduction of genetic material from another organism which produces a trasgenic of genetically modified organism

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Describe how a micro-organism is genetically modified

Circular plasmid extracted from bacteria and cut using restriction enzymes.Part of human gene spliced with plasmid.Placed into bacterial cell.Cells multiply in fermenter.Protein produced extracted

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How can foreign genes be inserted into plant cells?

1.Bacteria:when bacteria invade plant cells, genes from plasmid DNA are incorporated into chromosomes of new plant cell. 2.Pellets covered with DNA containing desired genes shot into plant cells using DNA gun 3.Viruses

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What is a marker gene?

A gene for antibiotic resistance

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Describe how a plant is genetically modified

New gene inserted into plant cell with a marker gene.Genes incorporated with plant gene.Incubated in growth medium with antibiotic.Only successful cells survive.Cells grown in sterile culture medium.Plantlets separated and grown into full sized plant

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Describe how an animal is genetically modified

1.DNA injected directly into nucleus of a fertilised egg.Egg implanted into surrogate female. 2.Retroviruses: incorporates its DNA into the hosts DNA

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Suggest reasons why it is much more difficult to introduce genes into eukaryotes

Eukaryotes contain a membrane bound nucleus

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What are some of the concerns about genetic modification?

Can transfer antibiotic resistance to microbes,transfer of viruses from animals to humans,formation of harmful products by new genes, transfer of genes to non-GM plants and increased chemical use in crops

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Biology unit 5 topic 8

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