Question 5
What is a gene, in chemical terms?
The right answer is the one marked above.
A length of DNA that controls one characteristic. A chromosome is one very long DNA molecule; a gene is a stretch of it, and the order of the bases along that stretch is the information.
This is the join between two earlier chapters: the one that said chromosomes carry the genetic material, and the one that said DNA stores it. They were describing the same object at different scales.