What explains differences in base composition between two regions of a chromosome?

What explains differences in base composition between two regions of a chromosome?

• A. They contain different genes
• B. They have different base sequences
• C. Both A and B
• D. They are located on different chromosomes

Answer: (C)

Base composition is about how much of each nucleotide—A, T, C, and G—exists in a DNA segment. Two regions on the same chromosome can have different base composition because their actual sequences differ. If the regions contain different genes, the sequences are typically different, which changes the balance of AT versus GC content in those regions. So, differences in base composition arise from having different base sequences, and those different sequences are usually tied to different genes, making both ideas explain the variation. The notion of being on different chromosomes isn’t needed here since we’re comparing regions within one chromosome.

Base composition is about how much of each nucleotide—A, T, C, and G—exists in a DNA segment. Two regions on the same chromosome can have different base composition because their actual sequences differ. If the regions contain different genes, the sequences are typically different, which changes the balance of AT versus GC content in those regions. So, differences in base composition arise from having different base sequences, and those different sequences are usually tied to different genes, making both ideas explain the variation. The notion of being on different chromosomes isn’t needed here since we’re comparing regions within one chromosome.