PATHOLOGY

Detailed explanation-1: -Transcription occurs in the nucleus whereas the major mRNA decay pathways operate in the cytoplasm. As synthesis and decay processes contribute equally to maintaining mRNA levels, it is quite likely that organisms have evolved a mechanism to coordinate events in the two compartments.

Detailed explanation-2: -In transcription, DNA is converted to mRNA. It takes place in the nucleus of a cell.

Detailed explanation-3: -The most prominent substructure within the nucleus is the nucleolus (see Figure 8.1), which is the site of rRNA transcription and processing, and of ribosome assembly.

Detailed explanation-4: -By housing the cell’s genome, the nucleus serves both as the repository of genetic information and as the cell’s control center. DNA replication, transcription, and RNA processing all take place within the nucleus, with only the final stage of gene expression (translation) localized to the cytoplasm.

Detailed explanation-5: -The processes of transcription and translation are physically separated by the nuclear membrane; transcription occurs only within the nucleus, and translation occurs only outside the nucleus in the cytoplasm. The regulation of gene expression can occur at all stages of the process (Figure 1).