Find the incorrect statement nucleoli

Correct Option: "only one nucleolus is found in the nucleus"

Explanation:
The statement "only one nucleolus is found in the nucleus" is incorrect because the number of nucleoli per nucleus is not strictly limited to one. The actual number varies depending on the organism, cell type, and metabolic state of the cell. For instance, human cells can have up to ten nucleoli during the early phases of the cell cycle before they coalesce into fewer, larger nucleoli. Cells that are highly active in protein synthesis often contain multiple nucleoli to facilitate the rapid production of ribosomes.

Here is why the other statements in the options are scientifically correct:
1. Nucleoli are synthesized around nucleolar organizing regions (NORs): NORs are specific chromosomal regions containing the genes that code for ribosomal RNA (rRNA). The nucleolus dynamically assembles around these chromosomal loci.
2. Transcription of rDNA occurs in the fibrillar center: The nucleolus is structurally divided into three components: the fibrillar center (FC), the dense fibrillar component (DFC), and the granular component (GC). The transcription of ribosomal DNA (rDNA) takes place at the interface of the fibrillar center and the dense fibrillar component.
3. Nucleolus contains a high concentration of iron in various plant species: In several plant species, the nucleolus is known to accumulate and store significant concentrations of iron, often bound to proteins, which is essential for nuclear and cellular functions.