Nucleic Acids in Key Cellular Structures

Steps:

• Identify nucleic acids as DNA (genetic material) and RNA (protein synthesis component).
• Locate DNA in the nucleus (main genome) and mitochondria (mtDNA for energy production).
• Locate RNA in ribosomes (rRNA for translation).
• Conclude that structures labeled 1 (nucleus), 2 (mitochondria), and 3 (ribosomes) all contain nucleic acids.

Why A is correct:

• Nucleic acids are defined as DNA and RNA; nucleus holds nuclear DNA, mitochondria hold mtDNA, and ribosomes hold rRNA, so all three sites contain them.

Why the others are wrong:

• B excludes mitochondria and ribosomes, ignoring their DNA and RNA.
• C excludes mitochondria, overlooking mtDNA essential for cellular respiration.
• D excludes nucleus, neglecting primary DNA storage for heredity.

Final answer: A