In contrast, there was a an effort to prevent hereditary blindness within the eugenics movement. Its proponents collected pedigrees, drafted legislation to prevent marriage of blind individuals, and surveyed ophthalmologists to assess causes of blindness and the cost to society to provide for the blind in specialized homes and schools. Their intent was to eliminate blindness in future generations. However, this was eugenics because affected individuals would not have been allowed to decide for themselves if the trait was undesirable, or what steps to take eliminate it.

Pedigree of a family with blindness

Explore the Eugenics Archive, especially the “Hereditary Disorders” topic, for many examples of how eugenicists viewed inherited diseases.

A quick search in the Eugenics Archive reveals some of the traits studied by Eugenicists:

Civic leadership
Musical ability
Dressmaking
Epilepsy
Dwarfism
Giantism
Carpentry
Deafness
Eye color
Insanity
Longevity
Shiftlessness
Cancer
Blindness
Albinism
Hemophilia
Boat building
Degeneracy
Poverty
Feeblemindedness
Cleft palate
Hare lip
Manic depression
Hair color, texture
Polydactyly
Height
Literary ability
Inventiveness
Color blindness
Mechanical skill
Artistic ability
Alcoholism
Thalassophilia (love of the sea)

Eugenicists failed to recognize that not all familial traits are biologically inherited, or that traits that are inherited can have complex causes. They did not consider that in addition to genes, families share customs, work environments, and eating habits that can affect their physical, mental, and emotional development.

Reading over the list, it is evident that Eugenicists were on target with some of their assertions. In my personal experience, my husband has long suffered from Thalassophilia, but my children have yet to express that trait. It must be recessive.

For further exploration:
From the Archive: Traits Studied By Eugenicists by Jan Witkowski, Cold Spring Harbor Laboratory
DNAftB Concept 14: Mendelian genetics cannot fully explain human health and behavior.

Why do we often see similar traits among parents and offspring? We inherit our DNA from our mother and father. This means we have half of our genes, or recipes, from our mom and half from our dad. Even with this basic idea, it can be confusing when we look at traits passed on through generations. Some terms to help include:

Genotype = the genetic information.

Phenotype = the physical trait expressed in the organism.

How are these terms useful or important? Let’s use flower color for an example. If you have a purple flower plant and you cross (mate) it with a while flower plant, what color do you expect to get in the offspring? You do not have enough information to answer that question. You were only given the physical traits of the plants, the phenotype. To accurately predict the color of the offspring you would need to know the genetic background of the parent plants, or their genotype.

It is important to keep in mind that genes do not blend with each other, even though sometimes it seems as though offspring have a blending of traits. Let’s think about it. Why is it important that genes do not blend? Genes are passed on intact from one generation to the next. This allows for phenotypes, or traits, to be expressed over long periods of time. If a trait provides an advantage for survival, it will most likely be passed on and accumulate over time. This process allows for life to continue. If the genetic information mixed every time offspring formed, we would not be here today.

(***Although genes don’t blend, they can mutate and change. That will be a topic for next time!)

I currently teach genetics and molecular biology to middle school students, high school students, teachers, and the general public. One of the greatest skills I have learned in my current position is the importance of engaging your audience and making the material you are introducing easy to understand. Instead of trying to impress people with fancy facts and complex ideas, I was taught to present information in a simple matter. In my initial observations of my fellow teachers, I was intimidated and thought that everyone around me had to be more intelligent. I heard one teacher describe the DNA in one cell as a cookbook and the genes as recipes. I was shocked at the simplicity of the analogy and went home to compare it with the complicated writing in my old textbooks. What I found was that the once foreign language of the textbooks was transformed. Not only could I grasp what they were saying with ease, but I was also able to identify the sections that were poorly explained. I felt empowered and began to search for new ways to describe biology in simple terms.

Getting the facts correct when teaching is equally important as enabling an audience to find a bridge between what they already know and what you are introducing them to. I continue to read about genetics from various resources and try to incorporate as much diversity into my lessons as possible. I enjoy using DNA from the Beginning to describe specific concepts and experiments. I recommend reading the descriptions and the checking out the animations for each section. Also, here are some of my favorite sites for introducing genetics and getting excited about DNA:

DNA interactive

The Human Genome Website: Genetics 101

American Museum of Natural History: The Gene Scene

For example, many genes are pleiotropic, meaning they affect more than one phenotype. How about the recent development on red heads and anasthetics? I happen to live with a red head, from a long line of red heads, so in our family this was a topic of discussion for days. The mutation that causes red hair, also induces the production of a hormone that stimulates a brain receptor associated with sensitivity to pain. In short, if you have red hair, you are likely to need more Novacaine at the dentist.

Dentists supposedly have known this for ages. I wonder how many other interesting pleiotropies like this one have been observed, and are touted as old wives-tales (or dentist tales, as it were), but may actually have scientific validity?