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Ch. 26 - Population and Evolutionary Genetics
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 26 - Population and Evolutionary GeneticsProblem 24
Chapter 26, Problem 24

Some critics have warned that the use of gene therapy to correct genetic disorders will affect the course of human evolution. Evaluate this criticism in light of what you know about population genetics and evolution, distinguishing between somatic gene therapy and germ-line gene therapy.

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Step 1: Define somatic gene therapy and germ-line gene therapy. Somatic gene therapy involves altering the genes in specific body cells of an individual, without affecting their reproductive cells, while germ-line gene therapy involves changes to the genes in reproductive cells (sperm or eggs), which can be passed on to future generations.
Step 2: Explain how somatic gene therapy affects evolution. Since somatic gene therapy changes only the non-reproductive cells, these genetic modifications are not inherited by offspring and therefore do not directly influence the gene pool or the course of human evolution.
Step 3: Discuss the potential evolutionary impact of germ-line gene therapy. Because germ-line gene therapy alters the DNA in reproductive cells, these changes can be transmitted to future generations, potentially affecting allele frequencies in the population and thus influencing evolutionary processes.
Step 4: Consider the role of natural selection and population genetics principles. Even if germ-line gene therapy introduces new genetic variants, their impact on evolution depends on factors such as selection pressures, genetic drift, mutation rates, and gene flow within the population.
Step 5: Evaluate the criticism by integrating these points. The concern about gene therapy affecting human evolution is more relevant to germ-line gene therapy than somatic therapy. However, the actual evolutionary impact depends on how widely germ-line modifications are adopted and how they interact with natural evolutionary forces.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Somatic Gene Therapy

Somatic gene therapy involves altering the genes in specific body cells of an individual to treat or prevent disease. These changes affect only the treated person and are not passed on to offspring, so they do not directly influence human evolution or the gene pool.
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Germ-line Gene Therapy

Germ-line gene therapy targets the reproductive cells (sperm or eggs), causing genetic changes that can be inherited by future generations. This type of therapy has the potential to alter the human gene pool and thus could impact the course of human evolution.
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Population Genetics and Evolution

Population genetics studies how gene frequencies change over time within populations due to factors like mutation, selection, and genetic drift. Evolution occurs when these gene frequencies shift, so interventions like germ-line therapy could influence evolutionary trajectories by changing heritable genetic variation.
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Evolution
Related Practice
Textbook Question

In an isolated population of 50 desert bighorn sheep, a mutant recessive allele c when homozygous causes curled coats in both males and females. The normal dominant allele C produces straight coats. A biologist studying these sheep counts four with curled coats. She also takes blood samples from the population for DNA analysis, which reveals that 17 of the sheep are heterozygous carriers of the c allele. What is the inbreeding coefficient F for this population?

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Textbook Question

To increase genetic diversity in the bighorn sheep population described in Problem 23, ten sheep are introduced from a population where the c allele is absent. Assuming that random mating occurs between the original and the introduced sheep, and that the c allele is selectively neutral, what will be the frequency of c in the next generation?

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Textbook Question

What genetic changes take place during speciation?

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Textbook Question

List the barriers that prevent interbreeding, and give an example of each.

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Textbook Question

What are the two groups of reproductive isolating mechanisms? Which of these is regarded as more efficient, and why?

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Textbook Question

A form of dwarfism known as Ellis–van Creveld syndrome was first discovered in the late 1930s, when Richard Ellis and Simon van Creveld shared a train compartment on the way to a pediatrics meeting. In the course of conversation, they discovered that they each had a patient with this syndrome. They published a description of the syndrome in 1940. Affected individuals have a short-limbed form of dwarfism and often have defects of the lips and teeth, and polydactyly (extra fingers). The largest pedigree for the condition was reported in an Old Order Amish population in eastern Pennsylvania by Victor McKusick and his colleagues (1964). In that community, about 5 per 1000 births are affected, and in the population of 8000, the observed frequency is 2 per 1000. All affected individuals have unaffected parents, and all affected cases can trace their ancestry to Samuel King and his wife, who arrived in the area in 1774. It is known that neither King nor his wife was affected with the disorder. There are no cases of the disorder in other Amish communities, such as those in Ohio or Indiana.

From the information provided, derive the most likely mode of inheritance of this disorder. Using the Hardy–Weinberg law, calculate the frequency of the mutant allele in the population and the frequency of heterozygotes, assuming Hardy–Weinberg conditions.

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