A Horns Activity: Writing Rules: Generalizing from data
Dragons have two different ways to express the horn genes. They can have horns or be "hornless." The rule for horns is:
HH, Hh, and hH gives horns, hh gives
1. Try to answer the following questions without looking at the computer. You may use the horns rule (above) as an example:
What is the rule for legs?
Dragons have three ways to express the
legs genes: 4, 2 and 0. The rule is LL for 4, Ll for 2 and ll for 0 legs.
What is the rule for wings?
We ask the student to recall what the
alleles for the different traits are and then to write a rule for that
trait. This builds on the previous exercise. The next direction takes the
kids to the computer to check their work and to make corrections when necessary.
The last two questions require multilevel thinking.
5. Why is it important to look at the similarities and differences? What does it mean to have different patterns of inheritance? Explain below.
The rule for horns is that H plus anything else gives horns, hh gives no horns. The rule for legs is LL gives 4 legs and ll none. (Incomplete dominance.) For wings, W plus anything else gives no wings, ww gives wings. All the traits except legs are examples of simple dominant/recessive rules.
Again, we are asking the student to
do something which is very hard. We are asking them to put into words the
differences or similarities between the different rules. Once they have
written their reasons down, they aren't through. They have to explain why.
In order to explain why, they must mentally review everything they have
learned about the relationship between two alleles for a trait and the
effect of that relationship on the phenotype of the organism. The fundamental
rules of genetics must be recalled and applied to each set of alleles,
since the mode of inheritance may differ from horns. And we wonder why
they have trouble articulating the answers to these questions!