Transcription Synthesizing RNA from a DNA Template

All cellular RNAs are synthesized from a DNA template through the process of transcription (IFigure 13.2). Transcription is in many ways similar to the process of replication, but one fundamental difference relates to the length of the template used. During replication, all the nucleotides in the DNA template are copied, but, during transcription, only small parts of the DNA molecule— usually a single gene or, at most, a few genes—are transcribed into RNA. Because not all gene products are needed at the same time or in the same cell, it would be highly

; are transcribed in both prokaryotic and eukaryotic cells.

^ .and some are produced only in eukaryotes.

Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

Pre-messenger RNA (pre-mRNA) Small nuclear RNA (snRNA) Small nucleolar RNA (sno-RNA) Small cytoplasmic RNA (scRNA)

Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

Pre-messenger RNA (pre-mRNA) Small nuclear RNA (snRNA) Small nucleolar RNA (sno-RNA) Small cytoplasmic RNA (scRNA)

copy RNA directly from RNA.

copy RNA directly from RNA.

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