In prokaryotic organisms, nuclear region is not surrounded by a membrane. This undefined nuclear region is known as
- (a)Nucleic acid
- (b)Nucleoid
- (c)Nucleolus
- (d)Nucleosome
Correct — B, Nucleoid. In prokaryotes (bacteria and archaea) there is no true membrane-bound nucleus; the genetic material sits in an irregular, undefined region of the cytoplasm called the nucleoid ('nucleus-like'). Because it lacks a nuclear envelope, it is not a real nucleus, which is exactly what the term nucleoid denotes.
- (a)Nucleic acid — Nucleic acids (DNA and RNA) are the molecules that carry genetic information, not the name of the cell region that contains them.
- (c)Nucleolus — The nucleolus is a dense body inside the eukaryotic nucleus where ribosomal RNA is made; prokaryotes have no nucleolus.
- (d)Nucleosome — A nucleosome is the basic packing unit of eukaryotic chromatin — DNA wound around histone proteins — not the prokaryotic nuclear region.
Prokaryotic cells lack membrane-bound organelles, including a true nucleus. Their single, usually circular DNA molecule lies free in the cytoplasm in a region called the nucleoid. Eukaryotic cells, by contrast, enclose their DNA within a nuclear envelope and contain sub-structures such as the nucleolus.
The four options are deliberately similar-sounding. Anchor each term: nucleoid = the prokaryotic 'nucleus-like' region; nucleolus and nucleosome are eukaryotic; nucleic acid is the molecule itself.
- Prokaryotes (bacteria, archaea) have no membrane-bound nucleus.
- Their genetic material occupies an undefined region called the nucleoid.
- The nucleolus is inside the eukaryotic nucleus and makes ribosomal RNA.
- A nucleosome is DNA coiled around histones — a eukaryotic chromatin unit.
Only the nucleoid is the membrane-less nuclear region of a prokaryote.
- Confusing nucleoid (region) with nucleolus (a eukaryotic sub-structure).
- Picking 'nucleic acid', which is the molecule rather than the nuclear region.
Asked as a definition-recall of the prokaryotic nuclear region, testing the near-identical 'nucleo-' terms.
No directly related past PYQ was found.
- practice — not a real PYQ
Which feature is characteristic of a prokaryotic cell?
- (a)A membrane-bound nucleus
- (b)A nucleoid without a nuclear membrane
- (c)Mitochondria with their own DNA
- (d)An endoplasmic reticulum
Answer(b) A nucleoid without a nuclear membrane — prokaryotes lack membrane-bound organelles.
- practice — not a real PYQ
The nucleolus, present in eukaryotic cells, is chiefly the site of
- (a)protein digestion
- (b)ribosomal RNA synthesis
- (c)ATP production
- (d)lipid storage
Answer(b) ribosomal RNA synthesis — the nucleolus assembles ribosomal subunits.