Question Video: Describing the Structure of Chromosomal DNA Biology • Third Year of Secondary School

Video Transcript

The majority of DNA in prokaryotes is chromosomal DNA. Which of the following best describes the structure of this chromosomal DNA? (A) Multiple small, circular loops of DNA. (B) A single, circular, double-stranded DNA molecule. (C) A short, linear, single-stranded DNA molecule. (D) A long, linear section of double-stranded DNA. Or (E) a threadlike section of DNA that has been coiled and condensed into an X shape.

DNA is generally a double-stranded molecule as shown here. Prokaryotes have the majority of their DNA in a single circular chromosome. They often also have multiple smaller loops of DNA known as plasmids. Plasmid DNA can carry additional genetic information that can be transferred between prokaryotes. However, this plasmid DNA is separate from chromosomal DNA.

Therefore, the answer that best describes the structure of prokaryotic chromosomal DNA is answer choice (B), a single, circular, double-stranded DNA molecule.