Tight junctions prevent the diffusion of: 

Macromolecules

Small water-soluble molecules

Ions

Membrane proteins 

Glycolipids

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#Id: 2548

#Unit 13. Methods in Biology

The sequence of the target DNA itself can affect PCR efficiency. The GC-rich sequences in target DNA may form secondary structures in the single strands produced by denaturation; this could reduce PCR efficiency.

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#Id: 2123

#Unit 8. Inheritance Biology

Pericentric inversion Chromosome inversion that includes the centromere in the inverted region.

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#Id: 8451

#Unit 1. Molecules and their Interaction Relevant to Biology

The diameter of a typical α helix is about 12 Å, which matches the 12 Å wide and 6–8 Å deep major groove of B-form DNA. 

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#Id: 10363

#Unit 4. Cell Communication and Cell Signaling

Type 2 T-independent

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#Id: 4948

#Unit 6. System Physiology – Plant

Phytochrome B (PhyB) is probably the photoreceptor involved in shade detection and avoidance. This response allows many species to greatly increase their stem extension rate when they become shaded by competitors.