Prokaryotic Genetics – Extra-Chromosomal DNA:\nSmall circular DNA molecules in the cytoplasm of many prokaryotes are known as:

Introduction / Context:
Beyond their main chromosome, many bacteria carry extra-chromosomal DNA elements important in gene transfer and antibiotic resistance.

Given Data / Assumptions:

• We are describing small, circular DNA molecules separate from the chromosome.
• They reside in cytoplasm and can be transferred between cells.

Concept / Approach:
These molecules are plasmids. They often carry accessory genes (e.g., resistance, virulence) and can replicate independently. Capsules are polysaccharide layers; nucleoids are chromosomal DNA regions; ribosomes synthesize proteins.

Step-by-Step Solution:
1) Match the description with known bacterial components.2) Rule out structures lacking DNA (capsule, ribosome).3) Identify plasmids as extra-chromosomal circular DNA.

Verification / Alternative check:
Plasmid cloning vectors used in biotechnology validate this identity.

Why Other Options Are Wrong:
Capsules are protective coats; nucleoid is main chromosome region; ribosomes contain rRNA/proteins, not free circular DNA.

Common Pitfalls:
Confusing plasmids with bacteriophages; phages are viruses, not cellular DNA circles.

Final Answer:
plasmids