Name _______________________________ Date _______________
Mutations Activity: Understanding the connection between changes in DNA and phenotype
GenScope File: Dragon
A mutation is an alteration in the DNA of an organism. When the DNA is changed, the action of the gene is changed and the resulting trait is different from the original.
Open GenScope using the Dragon file and click on the second button to produce a male dragon. Before you start messing around with the DNA, use the chromosome tool to bring up chromosome 1 which contains the horn gene. Click on the alleles on both chromosomes and refresh your memory about what happens to the organism with each combination of alleles.
What are the rules for horns?
Hh gives _______
hH gives _______
hh gives _______
The student should answer that HH, Hh and hH all give horns, hh gives no horns.
This exercise is designed to refresh the memory about a previous exercise. It requires the student to go back and forth between the chromosomes window and the organism window to observe what the effect on the phenotype is when the genotype is changed. This will reinforce the idea of cause and effect, we hope.
2. Now, do the same for wings. Write the rules for the inheritance of this trait, and test your answers. Hint: To test patterns of inheritance, the alleles should be combines in various combinations - like and unlike.
W W gives __________
W w gives __________
w W gives __________
w w gives __________
3. Now lets make a mutation. Using the chromosome tool, open up the chromosome window if it isn't already open. Click on the DNA button. The cursor will turn into a rectangular magnifying glass when it is passed over the chromosome. Center it over the Color A gene on the X chromosome and click. A new window, the DNA window, will appear. If you add some of the four bases (Adenine, Thymine, Cytosine, Guanine) or delete some, then click on the Apply button, you will create a mutation. Go back to the chromosome window and check the menu for the Color A allele on the chromosomes. There should be a new allele listed, aw. Change both alleles to aw and watch what happens to your dragon in the organism window. Now determine what the rule of inheritance is for the albino gene and write it in the space below. Do the same for wings.
To do this, test the mutated gene in
the same way that you tested the non-mutated genes: Change the menu for
the gene on the chromosome so that you have 2 alleles the same, 2 unlike
alleles, allele + mutated alleles and 2 mutated alleles. As you make the
changes on the chromosomes, watch what happens to the dragon in the organism
The full impact of the intricacy of color inheritance is finally felt here. Because color is polygenic (two genes, interacting, determine color in dragons) the inheritance pattern in necessarily complex. By watching the organism window as the allele combinations are changed, the student can see what the effect is. Of course, we must not forget to mention that the DNA window, a third level, is seen by the student as s/he manipulates the gene. In this way, s/he can actually see the effect of changing the DNA immediately - "up close and personal" - something that you can't do without a computer!
W W gives ____________
W w gives ____________
w W gives ____________
w w gives ____________
W ww gives ____________
w ww gives ____________
ww ww gives ____________
Aside from the fact that having wings is recessive, which is always jolting to the students, a new dimension is added in this problem. Having a double set of the ww allele causes the dragon to die. In real life, there are many mutations which are lethal. This is another case of trying to bridge the gap between the model and the real world.
4. Now, using this information, can you come up with a general rule which would apply to the inheritance of other mutations? Write it in the space below.
The most difficult task for almost everyone,
adult or student, is to take data and make a generalization from them.
By leading the kids through this exercise, we hope that they will get some
much needed practice. In this way, they should be able to make the jump
from modeling to real life.
F F, F f, F
f f, f- breathe fire
F ff, f ff, ff ff, ff - breathe blue fire
H h, HH
h h no horns
H hh, h hh, hh hh unicorn horn