Three-spined stickleback fish live in lakes formed when the last ice age ended 10,000 to 15,000 years ago. In lakes where the sticklebacks are prey for larger fish, they develop 35 bony plates along their body as armor. In contrast, sticklebacks in lakes where there are no predators develop only a few or no bony plates. Loss-of-function mutations in the coding region of the homologous gene in humans result in loss of hair, teeth, and sweat glands, as in the toothless men of Sind (India). What does this suggest about hair, teeth, and sweat glands in humans?

Verified step by step guidance

1. Understand the context: The problem describes a gene that influences physical traits in both stickleback fish and humans. In sticklebacks, the gene affects the development of bony plates, while in humans, loss-of-function mutations in the homologous gene result in loss of hair, teeth, and sweat glands.
2. Identify the genetic principle: The gene in question likely plays a role in the development of specific structures in both species. This suggests that the gene is conserved across species and has a similar developmental function.
3. Relate the gene's function to humans: In humans, the loss-of-function mutations indicate that the gene is essential for the proper development of hair, teeth, and sweat glands. This implies that these structures are dependent on the gene's activity during development.
4. Consider evolutionary implications: The presence of this gene in both sticklebacks and humans suggests that it has been conserved through evolution, highlighting its importance in the development of adaptive traits in different environments.
5. Conclude the significance: Hair, teeth, and sweat glands in humans are likely derived traits that evolved under the influence of this gene, and its loss-of-function mutations reveal its critical role in the formation of these structures.

Key Concepts

Natural Selection

Natural selection is a fundamental mechanism of evolution where organisms better adapted to their environment tend to survive and reproduce more successfully. In the case of the three-spined stickleback fish, those with more bony plates are favored in predator-rich environments, illustrating how environmental pressures shape physical traits over generations.

Genetic Mutations

Genetic mutations are changes in the DNA sequence that can lead to variations in traits. Loss-of-function mutations, like those affecting hair, teeth, and sweat glands in humans, can result in the absence or reduction of these features, highlighting the role of specific genes in the development of physical characteristics.

Homologous Genes

Homologous genes are genes that share a common ancestry and often retain similar functions across different species. The mention of a homologous gene in humans related to the stickleback's bony plates suggests that evolutionary adaptations can arise from modifications in similar genetic pathways, indicating a shared evolutionary history.