Two adjacent cells in the nematode worm nor-mally differentiate into an anchor cell (AC) and a ventraluterine precursor (VU) cell, but which of the two becomesthe AC and which becomes the VU cell is completely ran-dom: the cells have an equal chance of adopting eitherfate, but they always adopt different fates. Mutations ofLin12 alter these fates. In hyperactive Lin12 mutants, bothcells become VU cells, while in inactive Lin12 mutants,both cells become ACs. Thus, Lin12 is central to the deci-sion-making process. In genetic mosaics in which oneprecursor cell has the hyperactive Lin12 and the other pre-cursor has the inactive Lin12, the cell with the hyperactiveLin12 always becomes the VU cell and the cell with inac-tive Lin12 always becomes the AC. Assuming that one cellsends a signal and the other cell receives it, explain howthese results suggest that Lin12 encodes a protein requiredto receive the signal. Offer a suggestion for how the fatesof these two precursor cells are normally decided in wild-type worms.
Two adjacent cells in the nematode worm nor-
mally differentiate into an anchor cell (AC) and a ventral
uterine precursor (VU) cell, but which of the two becomes
the AC and which becomes the VU cell is completely ran-
dom: the cells have an equal chance of adopting either
fate, but they always adopt different fates. Mutations of
Lin12 alter these fates. In hyperactive Lin12 mutants, both
cells become VU cells, while in inactive Lin12 mutants,
both cells become ACs. Thus, Lin12 is central to the deci-
sion-making process. In genetic mosaics in which one
precursor cell has the hyperactive Lin12 and the other pre-
cursor has the inactive Lin12, the cell with the hyperactive
Lin12 always becomes the VU cell and the cell with inac-
tive Lin12 always becomes the AC. Assuming that one cell
sends a signal and the other cell receives it, explain how
these results suggest that Lin12 encodes a protein required
to receive the signal. Offer a suggestion for how the fates
of these two precursor cells are normally decided in wild-
type worms.
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