Which feature distinguishes eukaryotic from prokaryotic cells regarding DNA organization?

• A. Eukaryotic DNA is linear and housed in a nucleus.
• B. Eukaryotic DNA is circular and located in the nucleoid.
• C. Eukaryotic DNA is circular and located in organelles only.
• D. Eukaryotic DNA is linear but located in mitochondria only.

Answer: (A)

DNA organization in cells hinges on whether DNA is enclosed in a nucleus and whether chromosomes are linear. In eukaryotes, the genetic material is linear and housed inside a membrane-bound nucleus, with DNA packaged into chromatin on multiple linear chromosomes. This separation of genetic material inside a nucleus is a defining feature of eukaryotic cells.

Prokaryotes, by contrast, do not have a true nucleus. Their DNA is typically a single circular chromosome located in the cytoplasm within a region called the nucleoid, and they may carry small circular plasmids outside of this main chromosome. While organelles in eukaryotes like mitochondria (and chloroplasts in plants) contain their own DNA, that DNA is generally circular and represents only a portion of the genome, not the primary genetic material.

So the distinguishing feature described here—linear DNA housed in a nucleus—best captures the difference between eukaryotic and prokaryotic DNA organization.