If the posterior region of an early limb bud in a chicken embryo
1. Apoptosisa. involves the self-destruction of cellsb. is a developmental abnormality with no known genetic basisc. is a normal part of developmentd. Both a & c are true2. If the posterior region of an early limb bud in a chicken embryo (containing the ZPA)is excised and transplanted onto the anterior region of a limb bud in a second embryo,what would you predict would be the phenotype of the limb in the second embryowhen it has developed?a. it will have a normal limbb. it will have a limb with twinned digits organized as mirror images of each otherc. it will have a limb with two ventral surfaces (equivalent to two “palm” surfaces)d. it will have a limb with two dorsal surfaces (equivalent to two “back of hand”surfaces)3. For a neuron at its resting potential, the forces acting on potassium (K+) ions area. a concentration gradient pulling K+ inward & an electrical potential pulling K+outwardb. a concentration gradient pulling K+ outward & an electrical potential pulling K+outwardc. a concentration gradient pulling K+ outward & an electrical potential pulling K+inwardd. none, since no ions can move in or out of a neuron when it is at its restingpotential4. During the first part of an action potentiala. increasing numbers of Na+ channels open & the membrane potential eventuallymatches the Nernst potential for Na+b. increasing numbers of Na+ channels open & the membrane potential movestoward the Nernst potential for Na+ but doesn’t reach it because Na+ channels startto shut down and K+ channels start to openc. increasing numbers of K+ channels open & the membrane potential eventuallymatches the Nernst potential for K+d. increasing numbers of K+ channels open & the membrane potential moves towardthe Nernst potential for K+ but doesn’t reach it because K+ start to shut down andNa+ channels start to open5. When Na+ channels open in a neuron during an action potentiala. Na+ ions pour into the cell, but the relative Na+ concentrations inside & outsidethe cell are essentially unchangedb. Na+ ions pour into the cell, reversing the relative ion concentrations so that theNa+ concentration becomes higher inside the cell than outside the cell, causingdepolarizationc. the net charge throughout the cytoplasm inside the neuron shifts from negative topositived. both A & C are true6. Which of the following developmental processes occur in animal embryos, but not inplants?a. cell proliferationb. cell differentiationc. cell migrationd. expression of homeotic genes that regulate the identity of a body part7. At some synapses, neurotransmitters hyperpolarize (rather than depolarize) thepostsynaptic neuron, moving it farther away from the threshold for generating anaction potential. Which of the following neurotransmitter effects would hyperpolarizea postsynaptic neuron at resting potential?a. Opening K+ channels in the cell membraneb. Closing K+ channels in the cell membranec. Opening Na+ channelsd. Both a & b8. Homeotic fruitfly mutantsa. result from particular Hox gene mutations being expressed in the segmentsexhibiting mutant phenotypesb. have normally developed body parts in abnormal locationsc. have abnormally developed body parts in normal locationsd. Both A & B are true9. You are working in a clinic in Brazil when someone brings in a young woman whohas been having convulsions. They bring a sample of a plant she has been taking asherbal medicine. You immediately recognize it as a plant you know inhibits thesodium-potassium pump in neurons. You quickly take her blood and send it to thelab. They send you back an analysis which allows you to compare her values tonormal values:IonPionInside cellBlood (normal) Blood (your patient)K+11405.510Na+0.0215150150Cl-0.019125125You calculate the resting potential of your patient using the Goldmanequation:THERE SHOULD BE A LOG BEFORE THE PARENTHESES, BUTIT’S TOO TRICKY TO FIX THIS RIGHT NOW AND YOU DON’TNEED TO MEMORIZE THIS EQUATION ANYHOW…” P [K + ] + P [Na + ] + P [Cl − ] %outClinEmembrane = 62mV $ K + out Na’+−P[K+P[Na+P[Cl# KinNainClout &” 1*10mM + 0.02 *150mM + 0.01* 9mM %= 62mV $’ = −64mV# 1*140mM + 0.02 *15mM + 0.01*125 &a. (2 pts) Why does the term for chloride ion have the concentration inside inthe numerator whereas the terms for potassium and sodium have theconcentration inside in the denominator?b. (1 pts) What part of the Goldman equation is modified by particular typesof ion channels opening & closing?c.(2 pts) If the resting potential of a healthy person is -75 mV, why doesyour patient’s value make sense based on her blood results?d. Draw a line across the graph of a normal action potential, below, thatindicates your patient’s resting potential. Based on this result, why does itmake sense that yourpatient is havingconvulsions?11.IonConcentration insidecell+K150 mMNa+ 15 mMCl9 mMOthe 140 mMranionsConcentrationoutside5.5 mM150 mM125 mM40 mMa. Using the tabled numbers above, draw a cell (a circle will do!) and label theion concentrations inside and outside the cell.b. Use the Nernst equation to calculate the membrane potential for K+, Na+ andCl-ions, individually, in a warm-blooded vertebrate (assume a temperature of37 C, i.e.,Eion =⎛ [ion ]out ⎞62mV* log ⎜⎟z⎝ [ion ]in ⎠
