Final answer:
The genetic information of an organism is stored in the nuclei of eukaryotic cells, within the DNA. The nucleus governs cell activities by regulating gene expression. Ribosomes do not contain genetic material but synthesize proteins as instructed by the DNA.
Step-by-step explanation:
The genetic information that describes the characteristics of an organism is found in nuclei of eukaryotic cells, specifically within the DNA. The nucleus is a membrane-enclosed organelle responsible for housing most of a cell's genetic material. This material, encoded in the form of genes along the DNA strands, dictates the structure and function of the organism. Moreover, gene expression regulated by the nucleus determines the cell's activities, ultimately influencing the organism's traits. DNA is also present in other organelles like mitochondria, but in much smaller amounts, and this mitochondrial DNA only controls a limited set of genetic information.
Moreover, the RNA components of ribosomes are synthesized in the nucleolus, an area within the nucleus. This ties back to the function of ribosomes, which are the sites of protein synthesis in the cytoplasm. It's important to note that ribosomes themselves are not the holders of genetic information but are part of the cellular machinery that translates genetic code into functional proteins, as per instructions from the DNA.