In eukaryotic organisms, gene expression can be regulated at several steps during protein synthesis. The steps at which this regulation can occur include:
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Transcription - Regulation can occur at the level of transcription through the binding of transcription factors, enhancers, silencers, and other regulatory elements that influence the initiation of transcription.
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Post-transcription - After transcription, eukaryotic cells can regulate gene expression through processes such as RNA splicing, 5' capping, polyadenylation, and RNA interference (RNAi), which can affect mRNA stability and translation efficiency.
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Translation - Gene expression can also be regulated at the translation level, where the initiation of translation can be controlled by factors that bind to the mRNA and influence ribosome assembly and activity.
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Post-translation - After translation, proteins may undergo various modifications (e.g., phosphorylation, glycosylation, ubiquitination) that can affect their activity, localization, and stability, thereby regulating their function.
In summary, the steps of protein synthesis where eukaryotic organisms can regulate gene expression are:
- Translation
- Post-translation
- Post-transcription
- Transcription
Thus, all options listed apply for regulation of gene expression in eukaryotes.