|MadSci Network: Genetics|
"Genetics" is probably one of the tougher areas of biology for most students to grasp (yet it's one of the most important..). Thus it's heartening to see that you'd like to tackle the subject with such young children! I think a number of basic concepts can be illustrated in a manner that 2nd graders can understand and appreciate. I'll list a few easy-to-recognize traits. Before you show the kids the traits, I'd consider emphasizing the following points:
I'm guessing most 2nd graders will enjoy anything that lets them stick their tongues out in the name of education, so I'd try the tongue-rolling trait first:
Tongue rolling - stick your tongue out and see if you can roll the edges into a loop. This trait is *thought to be* dominant, meaning you only need one "working" copy of the gene to have it - Tt, or TT. I say "thought to be dominant" as there have been studies suggesting that the trait can be learned. Additionally, identical twins do not always share the tongue rolling trait - a piece of information which indicates that it may not be genetically controlled. I present it, however, as it is a simple test, and because most kids raise no objection to an opportunity to stick out their tongues.
If the students seem to be following along, you may want to work in the fact that the two copies of genes we receive from our parents are not necessarily identical. However, I'd emphasize the nature of observation in determining whether a person has a particular trait.
Hitchiker's thumb - Stick your thumb up, as though "thumbing" a ride. You have the trait if the first part of the thumb bends back more than 45 degrees. This trait is recessive meaning you need two copies of the gene to have it (hh).
Ear lobe attachment - See whether the ear lobes are attached to the side of the head, or whether they hang freely. Unattached earlobes are dominant to attached earlobes.
Widow's peak - People whose hair comes to a point over the middle of their forehead have a widows peak (a dominant trait).
A number of K-12 schools have online projects to collect data concerning genetic traits. Your students can use the WWW to submit their information to some of these projects.
If things can be discussed in more than one session, send the students home with a list of traits to see which ones their parents and siblings have. I'd create a table similar to the one below. When the students return it might be of interest to construct pedigrees of specific traits based on the information each person collected. I don't expect they'll follow all the nuances of inheritance, but it will at least illustrate the concept of where our genetic traits come from.
Person: Traits: Tongue rolling Hitchiker's thumb Ear lobes Widow's peak Me Mom Dad Bothers Sisters Grandparents Aunts Uncles Cousins..Making a pedigree:
In addition, the following sites may of help:
What are some traits in your family
Online Mendelian Inheritance in Man: At the NIH.
- Lynn Bry, MadSci Admin
Try the links in the MadSci Library for more information on Genetics.