Which of the following pairs of substances are found inside a mitochondrion?

Options

A. Single RNA molecule and 50S ribosomes
B. Single DNA molecule and 50S ribosomes
C. Single RNA molecule and 70S ribosomes
D. Single DNA molecule and 70S ribosomes

Answer

To solve the question of which pairs of substances are found inside a mitochondrion, we can analyze the options provided:

1. **Option 1: Single RNA molecule and 50S ribosomes.**
- Mitochondria do not contain 50S ribosomes; they have 70S ribosomes. Furthermore, while RNA is present in mitochondria, it is not typically referred to as a "single RNA molecule."

2. **Option 2: Single DNA molecule and 50S ribosomes.**
- Similar to option 1, mitochondria do not contain 50S ribosomes. They contain a circular DNA molecule, but the ribosome component is incorrect.

3. **Option 3: Single RNA molecule and 70S ribosomes.**
- While 70S ribosomes are indeed present in mitochondria, the presence of a "single RNA molecule" is not accurate in the context of what is typically found in mitochondria.

4. **Option 4: Single DNA molecule and 70S ribosomes.**
- This option correctly identifies that mitochondria contain a single circular DNA molecule (which is often referred to as mitochondrial DNA) and 70S ribosomes, which are involved in protein synthesis within the mitochondria.

Based on the analysis of each option, the correct answer is:

**Option 4: Single DNA molecule and 70S ribosomes.**