Genetic Determinism

What role do genes play in how organisms develop? John begins by distinguishing the genotype from the phenotype. Genetic determinism says that the genotype completely determines the phenotype, that is, the genes completely determine how an organism turns out. We often read about “a gene for intelligence” and “genes for homosexuality”, but what does that mean? Doesn’t that support the idea of genetic determinism?

John introduces the guest, John Dupre. Dupre distinguishes between various senses of the word “gene”. But, John asks, haven’t we found a gene for Down syndrome? Dupre explains what that phrase means. Ken says that he learned about the genetic code in school that spells out how each organism will develop. Dupre replies that that use of the phrase “genetic code” is incorrect. The genetic code is very basic and the phenotypic traits depend on more than just the genes. For example, Dupre says, a family may have a common nose shape, but that is determined by biology, not just the genes. Dupre gives some reasons for looking at the genome, as a whole, rather than individual genes. Ken summarizes: using the phrase “gene for X” does not mean that someone that has that gene will necessarily have X.

Ken asks aren’t genes distinctive, extra-powerful causes? The genome is important but overemphasized. Dupre criticizes the idea that all the information that is passed from parents to offspring is in the DNA. Dupre gives some reasons for looking at the genome as a whole rather than individual genes. Then, John, Ken, and Dupre discuss what it means when people talk about the number of genes in the human genome and what “junk DNA” is.

Dupre thinks that genetic determinism is false. Does this mean that anyone can become anything? What does his view entail? There are limits, but they are not imposed solely by genes. Dupre thinks we should shift from focusing on the genome to concentrating on development.

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