Read the given passage and answer the questions that follow:
In prokaryotes such as E. coli, though they do not have a defined nucleus the DNA is not scattered throughout the cell. The DNA is held with some proteins in a specific region. In eukaryotes this organisation is much more complex. There is a set of positively charged basic proteins called histones. Histones are organised to form a unit of 8 molecules called histone octamer. The negatively charged DNA is wrapped around the positively charged histone octamer.
What is the region called where negatively charged DNA is held with positively charged proteins in prokaryotes?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Nucleoid
Prokaryotes such as E. coli have no nuclear membrane. Their DNA is still not spread through the cell. Being negatively charged, it is held with some positively charged proteins in one region called the nucleoid. Here the DNA is arranged in large loops held by proteins.
Option (1) Nuclear envelope — Incorrect. A nuclear envelope surrounds the nucleus of eukaryotic cells. Prokaryotes do not have a defined nucleus, so they have no nuclear envelope.
Option (2) Nucleoid — Correct. The nucleoid is the region where the DNA of a prokaryote is held with positively charged proteins.
Option (3) DNA loop — Incorrect. The DNA in the nucleoid is organised in large loops, but a loop is a shape of the DNA, not the name of the region.
NCERT Extract:
Packaging of DNA Helix – “… In prokaryotes, such as, E. coli, though they do not have a defined nucleus, the DNA is not scattered throughout the cell. DNA (being negatively charged) is held with some proteins (that have positive charges) in a region termed as ‘nucleoid’. The DNA in nucleoid is organised in large loops held by proteins.”