Regarding DNA location and organelles, what is true?

• A. Eukaryotes have circular DNA and no nucleus.
• B. Eukaryotes have linear DNA in a nucleus and many membrane-bound organelles.
• C. Eukaryotes have circular DNA in a nucleoid.
• D. Eukaryotes have linear DNA without any organelles.

Answer: (B)

Eukaryotic cells organize their genetic material in a nucleus, where the DNA is linear and arranged into chromosomes. This nucleus is surrounded by a membrane, which helps keep transcription and RNA processing separate from translation. In addition, eukaryotes have many membrane-bound organelles that compartmentalize different cellular functions, like mitochondria and the endoplasmic reticulum. It’s also true that mitochondria (and chloroplasts in plants) contain their own circular DNA, but the main genome in the nucleus of eukaryotes is linear. The other statements don’t fit because they describe prokaryotic features: circular DNA located in a nucleoid without a true nucleus, or linear DNA but without organelles.