1. TOOTHPICK FISH

2. Purpose:
To model the relationships between many different aspects of fish life: genes, traits, variation, survival, and reproduction.

3. Materials:
1 “gene pool” container with 8 red, 8 green, and 8 yellow toothpicks.
Pencil/Composition Books

4. FISH COLOR (PHENOTYPE) GENE COMBINATIONS (GENOTYPE)
Data:
FISH COLOR (PHENOTYPE)
GENE COMBINATIONS (GENOTYPE)
GREEN
RED
YELLOW
ORANGE

5. Information: The GREEN (G) is dominant to all other color genes.
The RED (R) gene is recessive to green and co-dominant to yellow.
The YELLOW (Y) gene is recessive to green and co-dominant to red.
Co-dominant alleles result in an ORANGE color (which is actually incomplete dominance).

6. Table A: Gene Pairs and Resulting colors:
Genotypes
Phenotypes
1st
2nd
3rd
4th
Offspring
(example) GR
Green G 1 2 3 4 5 6 7 8 9 10 11 12

7. Table B: Offspring color Toothpick Generations
Environment
Generation
Green
Red
Orange
Yellow
Lots of Green Seaweed growing everywhere
1st
2nd
3rd
The seaweed dies and leaves bare rock and sand
4th
4th (survivors)

8. 1st Analysis:
Can two red fish mate and have green offspring? Why or why not?
Can two orange fish mate and have red offspring? Why or why not?
Can 2 green fish mate and have orange offspring? Why or why not?

9. Procedure:
Make a 1st generation of fish. WITHOUT looking pull out of your gene pool pairs of toothpicks.
Once you have your 12 pairs, record your data in Table A.
Count the #’s of each color and record in “1st Generation” in Table B.

10. Environment Change
The stream where the fish live is very green and lush with lots of vegetation and algae covering the streambed and banks. The green fish are very well camouflaged from predators in this environment and the red and orange fish fairly well also. However, none of the yellow fish survive or reproduce because predators can easily spot them in the green algae environment. (Any yellow fish – put to the side)

11. Procedure: Put all the remaining genes back in the “gene pool.”
Without looking, draw a 2nd generation of fish, record genes and color in Table A.
Count the #’s of each color and record in “2nd Generation” in Table B.
Set aside any yellow fish.

12. Environment
The well-camouflaged fish live longer and have more offspring, so their numbers are increasing. Draw toothpicks to make a 3rd generation of fish.
Record your data in Table, then write the total #’s of each color in the 3rd generation row of Table B.
Set aside any yellow fish
Return any survivors to the gene pool

13. 2nd Analysis: Have all the yellow genes disappeared?
Has the population size changed? In what way? Would you expect this to happen in the wild? Explain your answer.
How does the population in the 3rd generation compare to the population in the earlier generations?

14. Procedure:
Draw more pairs of genes to make a 4th generation of fish. Record your data in Tables A & B.
Do NOT remove yellow fish.

15. Oh-Oh!! Natural Disaster!!
Factory waste harmful to algae is dumped into the stream killing much of the algae very rapidly. The remaining rocks and sand are good camouflage for the yello, re, and orange fish. Now the green fish are easily spotted by predators and can’t survive or reproduce.
Set aside all green fish from the 3rd generation.
Record the surviving color of offspring in Table B (4th generation survivors row).