GRE Subject Test: Biochemistry, Cell, and Molecular Biology › Help with Nuclear Structure
What is the main function of the nucleolus in eukaryotic cells?
To promote the transcription, processing, and assembly of rRNA genes into ribosomes
To facilitate nuclear transport of proteins and mRNA from the nucleus to the cytoplasm
The site of microtubule assembly during mitosis
Eukaryotic cells do not have a nucleolus
Storage site for transcription factors, RNA polymerases, DNA polymerases, and other transcriptional machinery until transcription occurs
The correct answer is that the nucleolus is the site of ribsome synthesis and assembly. Chromosomes containing rRNA (ribosomal RNA genes) are clustered within the nucleolus, which facilitates rapid transcription and processing of rRNA genes and assembly of rRNA subunits into ribosomes.
The nuclear lamina is generally associated with __________.
chromatin containing transcriptionally inactive genes
chromatin containing transcriptionally active genes
ribosome synthesis and assembly
heterochromatin and transcriptionally active genes
euchromatin and transcriptionally inactive genes
The correct answer is chromatin and transcriptionally inactive genes. The nuclear lamina provides support and structure to the nucleus and binds transcriptionally inactive regions. Euchromatin is loosely packed chromatin and is, therefore, associated with transcriptionally active genes. Alternatively, heterochromatin is densely packed chromatin and implies inactive genes. Ribosome synthesis and assembly occurs in the nucleolus.