transcription is the synthesis of an RNA copy of a segment of DNA. RNA is synthesized by the enzyme RNA polymerase.
segment
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in a prokaryotic cell, transcription and translation are coupled; that is, translation begins while the mRNA is still being synthesized. in a eukaryotic cell, transcription occurs in the nucleus, and translation occurs in the cytoplasm.
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because there is no nucleus to separate the processes of transcription and translation, when bacterial genes are transcribed, their transcripts can immediately be translated.
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eu
transcription and translation are spatially and temporally separated in eukayotic cells; that is, transcription occurs in the nucleus to produce a pre-mRNA molecule.
the pre-mRNA is typically processed to produce the mature mRNA , which exits the nucleus and is translated in the cytoplasm.