Expression of class II molecules by B cells is down-regulated by IFN-¥.

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#Id: 10377

#Unit 4. Cell Communication and Cell Signaling

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#Id: 8861

#Unit 2. Cellular Organization

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#Id: 2149

#Unit 9. Diversity of Life Forms

Many phenotypic traits are genetically variable within species, they can readily evolve by natural selection and genetic drift.

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#Id: 3268

#Unit 3. Fundamental Processes

The Ames test uses a strain of S. typhimurium that is mutant for the operon responsible for the biosynthesis of the amino acid histidine. For example, the mutant operon might contain a missense or a frameshift mutation in one of the genes for histidine biosynthesis.

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#Id: 865

#Unit 13. Methods in Biology

The size of a PCR product is mainly determined by the binding location of the PCR primers.