What is a small cellular inclusion consisting of a ring of DNA capable of autonomous replication called?

A small cellular inclusion that consists of a ring of DNA capable of autonomous replication is known as a plasmid. Plasmids are typically found in bacteria and some archaea, and they can carry genes that provide advantages, such as antibiotic resistance or the ability to metabolize different substances. What sets plasmids apart from chromosomes is their circular shape and their ability to replicate independently of the chromosomal DNA within the cell. This characteristic is particularly useful in genetic engineering and molecular biology, where plasmids are often utilized as vectors to introduce foreign genes into host cells.

In contrast, chromosomes are linear structures that contain the bulk of genetic information in eukaryotic organisms and are not capable of independent replication like plasmids. Nucleotides are the building blocks of DNA and RNA, and cellular vectors typically refer to larger constructs or systems used for gene transfer, often incorporating plasmids. Thus, plasmids stand out due to their unique properties of autonomy and circularity.