4) Questions A-D below list four experimental conditions for sea urchin fertiliz

Question

4) Questions A-D below list four experimental conditions for sea urchin fertilization. Match each with one of the observed outcomes (1-5), and briefly explain each answer. (3pts each, 12 points) im 1. No effect, fertilization proceeds normally. 2. Polyspermy 3. Premature initiation of late events (all events beyond the fast and slow blocks to polyspermy 4. No cortical reaction. 5. No initiation of late events. im A) Fertilization in low Na+ sea water. B) Fertilization in normal sea water followed by transfer to Na+-free sea water. C) Fertilization in Ca++-free sea water. D) Treatment of eggs prior to fertilization with xestospongin C, a drug that interferes with nositol triphosphate (IP3) signaling.

Explanation / Answer

A)Premature initiation of events

1. tranfer in low sodium water show a rapid blokage to polyspermy

2.the fertilization potential gets affected decreases probability that extra sperm will enter egg.

3.it occurs due to change in membrane potential.

B) premature initiation of late events

1.no changes in normal sea water as it require mg for fertilization

2.but fertilization affected in no sodium water

3.as na required for motility and even respiration in sperms

C) no effect fertilization proceeds normally

1. ca is needed during fertilization for two processes: acrosomal reaction and corticle granule reaction.

2.but ca ions neeed for these reactions come from wihin the egg itself and not from external source.

3.so change in ca do not affect fertiliztion.

D)POLYSPERMY

1.results in oocyte activation

2.causes increase in ca level by intracellular activation

3/help in cortical rections and cause good fertilization.

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