Answer:
b. gene; DNA strand; chromosome; genome
Explanation:
The smallest unit in genetic structure will be gene which is a segment of DNA. After that comes DNA strand which may contain one or more genes. A chromosome is a larger structure as compared to a DNA strand because a chromosome contains two DNA strands which are joined at centromere. All the chromosomes in an individual collectively form genome so genome is an even larger term when it comes to genetic information.
