Recombination between the VH and D-JH segments follows during the pro-B-cell stage.

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#Id: 186

#Unit 5. Developmental Biology

A morphogenetic determinant specifies cells in a qualitative (“present or absent”) way.

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#Id: 187

#Unit 5. Developmental Biology

In the frog (Xenopus laevis)

A gradient of the paracrine factor activin (a morphogen), causes concentration-dependent expression differences of two genes in unspecified cells.

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#Id: 188

#Unit 5. Developmental Biology

At high concentrations (about 300 molecules/cell), activin induced expression of the goosecoid gene and instructed the cell to become the frog’s dorsal-most structures.

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#Id: 189

#Unit 5. Developmental Biology

Potency, commitment, specification, induction, competence, determination and differentiation; morphogenetic gradients; cell fate and cell lineages; stem cells; genomic equivalence and the cytoplasmic determinants; imprinting; mutants and transgenics in analysis of development

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#Id: 190

#Unit 5. Developmental Biology

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#Id: 191

#Unit 5. Developmental Biology

At slightly lower concentrations (intermediate concentrations), activin (about 100 molecules per cell) activated the Xbra gene and instructed the cell to become muscle.