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?

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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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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