**Question:** Both DNA and RNA are present in:

A. Nuclei
B. Mitochondria
C. Ribosomes
D. Chloroplasts

**Correct Answer:** A. Nuclei

**Core Concept:** DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid) are essential components of cells. DNA is the genetic blueprint of an organism, encoding the genetic information necessary for protein synthesis and cellular processes. RNA, on the other hand, plays a crucial role in translating the genetic information encoded in DNA into functional proteins.

**Why the Correct Answer is Right:** DNA is predominantly found within the cell's nucleus, which is the primary site for genetic information storage and regulation. The nucleus contains the genetic material of the cell, including the DNA that determines an organism's inherited traits and serves as the template for protein synthesis.

**Why Each Wrong Option is Incorrect:**

B. Mitochondria: Although mitochondria contain DNA, it is not the primary genetic material and is different from nuclear DNA. The mitochondrial DNA (mtDNA) encodes a limited set of proteins involved in mitochondrial functions, not the organism's overall genetic information or protein synthesis.

C. Ribosomes: Ribosomes are cellular organelles responsible for protein synthesis. While they do contain RNA (ribosomal RNA, or rRNA), the presence of DNA is not relevant to their function.

D. Chloroplasts: Chloroplasts are organelles found in plant cells responsible for photosynthesis. They contain chlorophyll, not DNA or RNA, which are associated with genetic information storage and protein synthesis, respectively.

**Clinical Pearl:** Understanding the cellular locations of DNA and RNA is crucial for understanding cellular functions and genetic processes. Knowing where these molecules are located helps medical students appreciate their roles in genetic information storage, regulation, and protein synthesis.