Question

which factor can change how genes are expressed without modifying the dna code itself? (1 point) a random dna replication error. the normal division of a somatic cell. an external environmental factor. the process of meiotic crossing-over.

Explanation:

• Option A: A random DNA replication error modifies the DNA code, so it's incorrect.
• Option B: Normal somatic cell division (mitosis) doesn't change gene expression without altering DNA code; it's about cell replication, not gene expression modulation, so incorrect.
• Option C: External environmental factors (like temperature, chemicals, diet) can affect gene expression through epigenetic mechanisms (e.g., methylation) without changing the DNA sequence, so this is correct.
• Option D: Meiotic crossing - over rearranges DNA segments (modifies the genetic code's arrangement), so it's incorrect.

Answer:

C. An external environmental factor.