What is pleiotropy, and how might it influence stickleback adaptation?

What is pleiotropy, and how might it influence stickleback adaptation?

• A. Pleiotropy means multiple genes affect one trait.
• B. Pleiotropy occurs when one gene affects multiple traits; it can constrain or facilitate adaptation if a gene affecting armor also influences other fitness-related traits.
• C. Pleiotropy is the random mutation of a trait.
• D. Pleiotropy only restricts evolution.

Answer: (C)

Pleiotropy is when one gene affects multiple traits. In sticklebacks, a single gene that controls armor plating can also influence other aspects of biology, like body shape or other fitness-related traits. Because of this, selection that favors less armor in a freshwater environment can bring along changes in these other traits as well. If those linked effects boost overall fitness, adaptation is facilitated; if they carry costs in other areas, adaptation can be constrained. This dual potential—that one gene’s effects can help or hinder overall fitness—explains how pleiotropy shapes stickleback evolution. The other descriptions misstate what pleiotropy is—they either describe multiple genes affecting one trait, or random mutation of a trait, or that pleiotropy only restricts evolution.

Pleiotropy is when one gene affects multiple traits. In sticklebacks, a single gene that controls armor plating can also influence other aspects of biology, like body shape or other fitness-related traits. Because of this, selection that favors less armor in a freshwater environment can bring along changes in these other traits as well. If those linked effects boost overall fitness, adaptation is facilitated; if they carry costs in other areas, adaptation can be constrained. This dual potential—that one gene’s effects can help or hinder overall fitness—explains how pleiotropy shapes stickleback evolution. The other descriptions misstate what pleiotropy is—they either describe multiple genes affecting one trait, or random mutation of a trait, or that pleiotropy only restricts evolution.