As students explore the concepts of genes and race, they are asked in the Motivation to reflect on their learning by completing the Race: Genes & Culture student sheet. This sheet provides answers to those questions.
1. What is a biological phenotype? Give an example from plants or animals of two different phenotypes of the same species.
Phenotype is the genetic expression that determines external, physical traits such as skin and hair color. Examples from nature of different phenotypes in dogs are golden retriever vs. English bulldog. In flowers, a rose has a different phenotype from a dandelion.
2. Are phenotypes the result of biology or a category made up by cultural groups?
They are the result of biology.
3. Are racial categories the result of biology, or are they groupings made up by cultural groups?
Racial categories are groupings made by cultural groups.
4. The Central Dogma of modern biology begins with: "DNA makes...." Complete the central dogma statement. Explain in your own words what it means.
DNA makes RNA makes proteins. It means that genes control the external phenotype through the internal DNA instructions given to RNA, which translate them into specific proteins that control specific cellular processes.
5. What does the phrase "gene expression" mean?
A gene is expressed when it is "turned on" to actively make proteins. Genes that are off are still healthy and may be passed on to the next generation—and expressed there.
6. Explain the evolutionary advantage of pigmented skin for people living in equatorial regions, such as Africa.
Dark skin is a genetically controlled evolutionary advantage that provides protection from the damaging UV radiation of equatorial locations. This protection is a survival advantage, which is also an evolutionary advantage enabling those with this protection to live long enough to reproduce.
7. Explain how twin girls can have the same biological parents, but look like they are from different parts of the world. In your answer, be sure to use these four terms: phenotype, gene expression, evolution, and survival advantage.
The twin girls can have the same genes but look different—have different biological phenotypes, where one is dark skinned and one is light skinned—because the gene expression is different in each. In the light-skinned twin, genes that code for skin pigment melanin are not expressed. In both the girls' ancestors, this trait of dark skin was a survival advantage that, through thousands of years of evolution, came to protect them from the harmful effects of UV radiation.