Just as anatomical homology can lead to vestigial structuressuch as human wisdom teeth and the wings of flightlessbirds, genetic homology can lead to vestigial DNA sequences.For example, most mammal species produce an enzyme,L-gulonolactone oxidase, that catalyzes the last step in the productionof vitamin C. The species that produce the enzyme areable to do so because they all inherited the gene that encodesit from a common ancestor. Humans, however, do not produceL-gulonolactone oxidase, so we can’t produce vitamin C ourselvesand must consume it in our diets. But even though wedon’t produce the enzyme, our cells do contain a stretch of DNAwith a sequence very similar to that of the enzyme-producinggene present in rats and most other mammals. The human version,though, does not encode the enzyme (or any protein). Weinherited this stretch of DNA from an ancestor that we share withother mammal species, but in us, the sequence has undergonea change that rendered it nonfunctional. (The change probablydid not confer a strong disadvantage, because our ancestors gotsufficient vitamin C in their diets.) The nonfunctional sequenceremains as a vestigial trait, evidence of our shared ancestry.Vestigial traits are evidence of both shared ancestry and changein traits over time. What kinds of observations and experimentsshow that natural selection contributes to evolutionary change?
Just as anatomical homology can lead to vestigial structuressuch as human wisdom teeth and the wings of flightlessbirds, genetic homology can lead to vestigial DNA sequences.For example, most mammal species produce an enzyme,L-gulonolactone oxidase, that catalyzes the last step in the productionof vitamin C. The species that produce the enzyme areable to do so because they all inherited the gene that encodesit from a common ancestor. Humans, however, do not produceL-gulonolactone oxidase, so we can’t produce vitamin C ourselvesand must consume it in our diets. But even though wedon’t produce the enzyme, our cells do contain a stretch of DNAwith a sequence very similar to that of the enzyme-producinggene present in rats and most other mammals. The human version,though, does not encode the enzyme (or any protein). Weinherited this stretch of DNA from an ancestor that we share withother mammal species, but in us, the sequence has undergonea change that rendered it nonfunctional. (The change probablydid not confer a strong disadvantage, because our ancestors gotsufficient vitamin C in their diets.) The nonfunctional sequenceremains as a vestigial trait, evidence of our shared ancestry.Vestigial traits are evidence of both shared ancestry and changein traits over time. What kinds of observations and experimentsshow that natural selection contributes to evolutionary change?
Biology: The Unity and Diversity of Life (MindTap Course List)
14th Edition
ISBN:9781305073951
Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr
Publisher:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr
Chapter26: Human Evolution
Section: Chapter Questions
Problem 1DAA: Neanderthal Hair Color The MC1R gene regulates pigmentation in humans (Sections 14.1 and 15.1...
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Just as anatomical homology can lead to vestigial structures such as human wisdom teeth and the wings of flightless birds, genetic homology can lead to vestigial DNA sequences. For example, most mammal species produce an enzyme, L-gulonolactone oxidase, that catalyzes the last step in the production of vitamin C. The species that produce the enzyme are able to do so because they all inherited the gene that encodes it from a common ancestor. Humans, however, do not produce L-gulonolactone oxidase, so we can’t produce vitamin C ourselves and must consume it in our diets. But even though we don’t produce the enzyme, our cells do contain a stretch of DNA with a sequence very similar to that of the enzyme-producing gene present in rats and most other mammals. The human version, though, does not encode the enzyme (or any protein). We inherited this stretch of DNA from an ancestor that we share with other mammal species, but in us, the sequence has undergone a change that rendered it nonfunctional. (The change probably did not confer a strong disadvantage, because our ancestors got sufficient vitamin C in their diets.) The nonfunctional sequence remains as a vestigial trait, evidence of our shared ancestry. Vestigial traits are evidence of both shared ancestry and change in traits over time. What kinds of observations and experiments show that natural selection contributes to evolutionary change? |
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