Here's why:

* DNA: Prokaryotic cells lack a nucleus, so their DNA is located in a region called the nucleoid. The nucleoid is not membrane-bound, but the DNA is organized and condensed within the cytoplasm.

* RNA: RNA is transcribed from the DNA in the nucleoid and then used for protein synthesis. This process occurs in the cytoplasm, where ribosomes are located.

So, while both DNA and RNA are within the cytoplasm, DNA is specifically concentrated in the nucleoid.