1. Testing how AB.a and AB.p differentiate. Early blastomeres in C. elegans Ther
ID: 190364 • Letter: 1
Question
1. Testing how AB.a and AB.p differentiate. Early blastomeres in C. elegans There are four cells in the early C. elegans embryo: AB.a, AB.p, EMS, and P2, whose spatial relationships are shown correctly at the right (anterior is to the left in the diagram) AB.a and AB.p are daughter cells of Pi, and EMS and P2 are daughter cells of P1. Jim Priess, Craig Mello, and Bruce Bowerman developed ways to manipulate blastomeres in the early embryo. They found they could move cells around by pushing them with a blunt needle, so that AB.a could be moved to lie in the position normally occupied by AB.p. They also developed ways to remove cells from the embryo by sucking them out of the eggshell with a pipette. AB ABp ABal MSE EMS Jim believed that P2 normally sends an inductive signal to the AB daughter it is touching that leads that AB daughter to form posterior pharynx. Using the simple blastomere manipulations Jim developed, describe one experiment you could perform to show P2 contact is sufficient to induce either AB daughter cell to form posterior pharynx. Craig Mello and Jim Priess created the embryo below on the right (b). A normal embryo is shown for comparison (a). If Jim's hypothesis above is correct, will this embryo make more or less anterior pharynx than normal? Clearly state your reasoning P2 P2 EMS EMSExplanation / Answer
a.From the figure we can see that P2 is touching ABp daughter cell that induces posterior pharynx formation.We can change the position of P2 such that it touches ABa daughter cell or shift ABa to ABp position such that ABa is in touch with P2. ABa daughter cells should now be able to make posterior pharynx.ABp since it loses contact with P2 would now go on to make anterior pharynx and not posterior pharynx..
b.It will make more of anterior pharynx than normal as P2 is neither in touch with ABa nor with ABp as a result of which induction of posterior pharynx would be less.
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