Definition

1. Noun:
   • A specific chromosomal region: The "nucleolus organiser" is the particular part of a chromosome that is associated with a nucleolus after nuclear division. It contains the genes for ribosomal RNA (rRNA) and is the site where the nucleolus forms.

Usage

• The term is used in cell biology and genetics to describe a functional region of a chromosome.
• It is a countable noun. Example: "The nucleolus organiser regions on these chromosomes are highly active."

Examples

• Noun:
  • Scientists studied the nucleolus organiser to understand ribosome synthesis.
  • Mutations in the nucleolus organiser can disrupt the formation of the nucleolus.

Advanced Usage

• "Nucleolus organiser region (NOR)": This is the full technical term often abbreviated as NOR. It refers to the chromosomal segment containing the rRNA genes.
  • The nucleolus organiser region is visible under a microscope after specific staining.

Variants and Related Words

• Nucleolus organizer: An alternative spelling, primarily used in American English.
• NOR (abbreviation): A common abbreviation for "nucleolus organiser region."

Synonyms

• NOR (Nucleolus Organiser Region): The abbreviated form is often used synonymously.
• Ribosomal DNA (rDNA) locus: While not perfectly identical, this term refers to the specific DNA sequences within the nucleolus organiser that code for rRNA.

Notes on Meaning

• The term specifically denotes a or on a chromosome, not the nucleolus itself. Its primary function is to organise the formation of the nucleolus, a sub-structure within the cell nucleus.

Noun

1. the particular part of a chromosome that is associated with a nucleolus after nuclear division