AP BIOLOGY

Detailed explanation-1: -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. As discussed in the preceding chapter, cells require large numbers of ribosomes to meet their needs for protein synthesis.

Detailed explanation-2: -mRNA, tRNA, rRNA are produced in the cell nucleus by transcription and get transferred to the cytoplasm for protein synthesis on ribosomes.

Detailed explanation-3: -The nucleolus is the most prominent structure in a cell nucleus. It is the site of ribosomal RNA (rRNA) transcription, pre-rRNA processing and ribosome subunit assembly.

Detailed explanation-4: -tRNA transcription and initial end processing occurs in the nucleolus. Following various modification steps in the nucleoplasm and at the inner nuclear membrane, intron-containing pre-tRNAs are exported to the cytoplasm via the Losl exportin and at least one unknown pathway.

Detailed explanation-5: -Ribosomal RNA (rRNA) is the most common form of RNA found in cells – it makes up around 50% of the structure of the ribosomes. It is produced in the nucleus, before moving out into the cytoplasm to bind with proteins and form a ribosome. Transfer RNA (tRNA) is found in the cytoplasm and has a complex shape.