Are repressive proteins involved in positive gene regulation?

In prokaryotes, a well-known activator protein is the catabolite activator protein (CAP), involved in positive control of the lac operon. In the regulation of gene expression, studied in evolutionary developmental biology (evo-devo), both activators and repressors play important roles.

Explanation:

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a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

a symbiotic relationship with the mitochondria