AP BIOLOGY

Detailed explanation-1: -Transport of messenger RNA (mRNA) from the nucleus to the cytoplasm is an essential step of eukaryotic gene expression. In the cell nucleus, a precursor mRNA undergoes a series of processing steps, including capping at the 5’ ends, splicing and cleavage/polyadenylation at the 3’ ends.

Detailed explanation-2: -The process of making mRNA from DNA is called transcription, and it occurs in the nucleus. The mRNA directs the synthesis of proteins, which occurs in the cytoplasm. mRNA formed in the nucleus is transported out of the nucleus and into the cytoplasm where it attaches to the ribosomes.

Detailed explanation-3: -Whereas many proteins are selectively transported from the cytoplasm into the nucleus, most RNAs are exported from the nucleus to the cytoplasm.

Detailed explanation-4: -The mRNP complexes move freely by Brownian diffusion at a rate that assures their dispersion throughout the nucleus before they exit into the cytoplasm, even when the transcription site is located near the nuclear periphery. The diffusion of mRNP complexes is restricted to the extranucleolar, interchromatin spaces.

Detailed explanation-5: -The molecular mechanism for axonal mRNA transport involves the recognition of zipcodes by RNA-binding proteins, assembly into RNA granules, and transport along the microtubules and actin filaments in the axon and growth cone.