Final answer:
Genes encoding for ribosomal RNAs and histones are located in the nucleus of eukaryotic cells, specifically within the nucleolus where rRNA is transcribed and ribosomes are assembled.
Step-by-step explanation:
Genes that encode for ribosomal RNAs and histones are typically identical to one another and located in tandem arrays within the nucleus of eukaryotic cells. This is because the nucleolus, a specialized structure within the nucleus, is the site where ribosomal RNA (rRNA) is transcribed, processed, and assembled into ribosomes. The rRNA genes are transcribed by RNA polymerase I in the nucleolus.
The histone genes, which are responsible for packaging DNA into structural units called nucleosomes, are also located in the nucleolus of the nucleus. These tightly packed forms of DNA make up chromosomes, which are found inside the nucleus as well. It's in the nucleolus where components essential for protein synthesis are produced, and then these components are exported to the cytoplasm where ribosomes, either free or attached to the rough endoplasmic reticulum, synthesize proteins.
Therefore, the correct answer to the given question is 1) Nucleus.