While most students don’t fully grasp this idea, there are a few examples we can use that can help to explain this.  I have always used examples of giraffes and the development of long necks, or antibiotic resistance in bacteria, but these seem to be a bit out of the realm of many 5^th grade students.  So what better example than ourselves!

During another lesson, I introduced the development of lactase persistence, or having the ability to drink and eat dairy products past infancy.  Digesting the sugar in milk (lactose) is dependent on whether or not the cells of your small intestine are producing the enzyme lactase.  Lactase is responsible for breaking lactose into smaller components that then get absorbed into the bloodstream.  For mammals that get milk from mother early in life, this enzyme is essential.  Would a mutation in the DNA that would allow a cell to continue to make lactase past infancy be beneficial?  It all depends on which population of humans you ask.

If it is a population of humans that began drinking the milk of other animals after the development of agriculture, like those of Northern European descent, it would be selected for.  These populations now show the highest frequency of lactase persistence among all human populations.  If dairy was not a part of your diet after infancy, this mutation wouldn’t be considered beneficial and would not have been selected for, such as in African, Asian and South American populations.

So, when teaching evolution and the changes that we see in species over time, it is nice to be able to give an example that we can see in humans.  Using an example that is a recent development in humans over the last 10,000 years, may help students to understand this concept better, and apply it across any species.

I happen to work at an institution where evolution is revered as the underlying theme that explains life and all of its processes.  For a biology teacher it’s a comfortable place to be.  I suppose I am spoiled. When I travel to schools, I am on occasion told by teachers how happy they are that I am presenting evolution for them.  It is a required part of the New York State science curriculum, but some of the teachers who are supposed to teach it, don’t want to.   It makes me wonder.  Are they uncomfortable with the science?  Are they afraid of parents or students lashing out at them?  Does the scientific theory of evolution somehow conflict with their religious beliefs?   I don’t know the answer.  I’m sure it’s a combination of several factors. 

My gut feeling is that most teacher reticence is due to lack of understanding.   I would feel very uncomfortable if asked to teach a topic I didn’t fully understand, and unfortunately this is what’s happening.   I think we need better teacher training, especially for elementary teachers who receive very little training in science.  Everyone who receives a degree in general education or in science education should have to complete a course in basic genetics and/or evolution.   This would significantly reduce the negativity associated with teaching evolution, and could help produce much happier teachers!

I have to remind myself that the students I work with have a lot of interesting ideas and can gain a lot from the ideas in science. It helps me to think about how exciting it can be to learn about DNA and proteins for the first time. I remember all of the negative experiences I have had as a student and how I can offer a better option for those I teach. I look out at their faces and remember just how hard it is to grow up. Not only are they learning new ideas in school and being tested, they are trying to figure out who they are and how they fit in. I guess what this does for me is break my focus on the negative and allows me to see what is right in front of me with a clear perspective. I hate getting caught up in myself because the greatest feeling I have is when I know that my energy today has helped someone. Maybe I just encouraged them to participate in class or showed them how they can understand more than they thought they were capable of, but that is important to me.

As teachers we become exhausted and burnt out if we allow ourselves to stop seeing all the reasons we love what we do. There are days when it is hard for me to remember and I need to have other teachers help me. I would be grateful to have you share your ideas. What do you do to stay positive and have fun?

Interestingly enough, the Spruce, a very common Christmas tree species, has seven times more DNA than a human. How is that, you say?  They are but simple trees, and we are complex animals with skills and intellect beyond compare! Well, you may not say that, but my students do! I shared that little gem with my class today, and they were shocked.

It turns out that all conifers like the Spruce, have 12 chromosomes (humans have 46), but they are really big. Scientists aren’t sure why this is so, but some speculate that this large amount of DNA may be how they have been such a successful plant, surviving for millions of years. There are several plant species that have way more DNA than we do, which brings to light the questions: Does more DNA make an organism more complex? Could a plant be more complex than a human? I suppose that depends on who you ask.

What I do know is that I love my Christmas tree, and all 12 of its giant chromosomes!

To read more about the Spruce geneome project in Sweden, go to: http://www.innovations-report.com/html/reports/agricultural_sciences/christmas_tree_times_dna_time_map_145376.html

Demonstrations with this wheel have led to some very interesting student responses and questions.  I have been accosted in the museum by students who believe that the wheel has actually predicted what gender their children will be, and even how many they will have!  This has led me to beat them to the punch during my demonstration, by explaining that the wheel is not a predictor of the future!

I have also been asked by concerned 10-year-olds, how much DNA their parents could possibly have left over after having 4 children? This one is a favorite of mine. When you really think about it, that thought makes perfect sense. Unless you’ve learned about meiosis and sex cells, how would you know that there are special cells, each containing extra copies of the genetic information to be passed on to children? In avoidance of these “uncomfortable” topics, some children are somewhat mislead when they begin learning about inheritance.

When I work with 5^th graders and discussions of 46 chromosomes per cell come up, I always add that some cells have no DNA (mature red blood cells) and some cells have only 23 chromosomes.  Inevitably, someone will ask why, and if they don’t I do! There are special cells that are used for reproduction, and when two of these cells unite, from a mother and a father, a full set of chromosomes is created. Covering this basic concept without the burden of meiosis, is perfectly suitable for 10-year-olds, and eliminates confusion.o

So how can you take this material from the television screen into the classroom? Using the applications of DNA testing alone can provide you with a wide range of lessons, including the use of DNA profiling, studying human origins, and solving mysteries of the past. One lesson that I have been teaching to a wide range of students in the 5^th-8^th grades, is the Mystery of Anastasia Romanov.

This lesson provides the opportunity to incorporate history into a science lesson, along with current trends in forensic science including anthropology and DNA testing. Many aspects of the biology curriculum are also involved, including reading pedigree charts, maternal inheritance of mitochondrial DNA, and DNA sequencing. It is a true interdisciplinary lesson that gets the students involved and interested, as they are asked to solve the mystery.

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?