DNA lesions that cause large distortions in the helical structure of DNA generally are repaired by the nucleotide-excision system, a repair pathway critical to the survival of all free-living organisms. 

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#Id: 7333

#Unit 11. Evolution and Behavior

When a population is in Hardy-Weinberg equilibrium, the genotypic frequencies are determined by the allelic  frequencies.

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#Id: 9619

#Unit 4. Cell Communication and Cell Signaling

HER2 (mouse Erb-B2), cannot bind any ligand, it can form a heterodimer with ligand-activated HER1, HER3, or HER4 (Erb-B1, 3, or 4)

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#Id: 661

#Unit 3. Fundamental Processes

Drosophila telomeres are an exception, consisting of terminal arrays of retrotransposons.

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#Id: 5211

#Unit 7. System Physiology – Animal

Activated protein C (APC), along with its cofactor protein S, inactivates factors V and VIII and inactivates an inhibitor of tissue plasminogen activator, increasing the formation of plasmin.

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#Id: 8127

#Unit 1. Molecules and their Interaction Relevant to Biology

β-Carotene is the precursor of vitamin A1.
Oxidation at C-15 converts retinol to the aldehyde, retinal, and further oxidation produces retinoic acid, a hormone that regulates gene expression.