The coexistence of multiple alleles at a locus in a population is called genetic polymorphism. A locus is usually defined as polymorphic if two or more alleles are present at a frequency of more than 1% in the population.

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#Id: 4783

#Unit 5. Developmental Biology

ABa and ABp are equivalent cells whose fates are determined by their positions in the embryo (if one experimentally reverses the positions of these two cells, their fates are similarly reversed and a normal embryo forms)

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#Id: 4784

#Unit 5. Developmental Biology

In an unperturbed embryo, both ABa and ABp contact the EMS blastomere, but only ABp contacts the P2 cell.

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#Id: 4785

#Unit 5. Developmental Biology

The P2 cell produces juxtacrine protein APX-1(a Delta homologue)

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#Id: 4786

#Unit 5. Developmental Biology

APX-1 is received by GLP-1 on the ABp cell

 

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#Id: 4787

#Unit 5. Developmental Biology

The GLP-1 protein (a Notch homologue) which is present on both the ABa and ABp cells

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#Id: 4788

#Unit 5. Developmental Biology

P2 cell establishes the

dorsal-ventral axis of C. elegans and confers on the ABp blastomere a fate different from that of its sister cell.