How are DNA and RNA like blueprints?
DNA and RNA are like blueprints because they contain genetic material. This genetic material is what makes more cells with the same material.
In Eukaryotes, DNA is contained within the nucleus to protect it from degradation. This means that the DNA should remain protected, as a "master copy" of the blueprints for proteins. mRNA is necessary because DNA cannot leave the nucleus, but RNA can. The use of mRNA means that the DNA can remain in the nucleus, while the RNA goes to the ribosomes for translation.
The nucleus is the control center of a cell. It contains the 'blueprints' called DNA. Along with the DNA you'll also find the nucleulus, histones, which help to pack the DNA, along with a variety of other proteins/enzymes (including RNA polymerases), transcription factors and some RNA. There are also other parts like a nucleolous