Cells can progress from totipotent to pluripotent to determined.   d development.

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#Id: 1601

#Unit 5. Developmental Biology

If Wnt PCP pathway is blocked, the mesoderm and endoderm form peripherally instead of centrally.

 

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#Id: 7682

#Unit 1. Molecules and their Interaction Relevant to Biology

In fig, Phi is fixed at 0º. Clashes occur at ALL Psi angles. Phi = 0º is physically

impossible.

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#Id: 4558

#Unit 8. Inheritance Biology

Comb shapes in chickens

9/16 walnut (R- P-)

3/16 rose (R- pp)

3/16 pea (rr P-)

1/16 single (rr pp)

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#Id: 6077

#Unit 10. Ecological Principles

Vulnerability to extinction can be linked to species characteristics

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#Id: 1588

#Unit 5. Developmental Biology

Primitive Streak

First arises from a local thickening of the epiblast at the posterior edge of the area pellucida (Koller’s sickle)

By stage 2, the primitive streak cells form a third layer that lies between the hypoblast and epiblast cells.

 By stage 3, the primitive streak has become a definitive region of the epiblast, with cells migrating through it to become the mesoderm and endoderm.