Dolphin Genetics
** All photos taken by Jamie Brusa under GA LOC permit No. 16104
Purpose of Lesson
Students will practice using Punnett Squares, calculating probabilities based on
Punnet Square results, and will become more familiar with genetic terms.
Performance Objectives
This lesson fits the grade seven topic, “Cells and Heredity.”
1.
Students will be able to utilize the scientific method to solve a given problem
(meets South Carolina standard 7-1.2)
2.
Students will analyze data (meets South Carolina standard 7-1.5)
3.
Students will practice using Punnett squares to predict the outcomes of monohybrid crosses (meets South Carolina standard 7-2.6)
4.
Students will analyze their conclusions drawn from the graph (meets South
Carolina standard 7-1.6)
5.
Students will practice using the terms dominant and recessive (meets South
Carolina standard 7-2.5)
Materials
Each student will need a dolphin card, which contains a photograph of a dolphin, a family symbol (such as square, circle, triangle...), the name of the dolphin, an age class (adult or calf), the gender, and a genotype.
Description of Activity
Students will complete the “Pre-Activity” worksheet.
The class will be given a quick review of how to perform and interpret the results of a Punnet Square.
Each student will be given a random dolphin card. The students will find their group members by finding other students with the same symbols on their cards.
Each group will consist of a female adult, a male adult, and at least one calf as their offspring. The students will work together in their groups to determine the probability that the calf dolphin would have the genotype given on the card based on the genotypes of the parents by using a Punnett square. Each group’s information will be summarized in a data table, which can be written on the board or in Excel and projected onto a screen. To save time and retain the students’ attention, all of the information except the probability of the calf genotype should

already be filled in, and each group can enter their information for that column once they have finished their Punnett Square and determined the probability of the calf being the genotype given on the card.
The students will then read the written problem on their worksheet to give context to the genotypes.
After all of the class data has been posted on the board, the students will construct a bar graph to represent the percentage of the population that has the dominant phenotype versus the recessive phenotype. The graph should have the genotype on the x-axis and the percentage on the y-axis. The students will also draw the conclusion, the population will/will not survive because __?__% of the dolphins have genotype, bb.
Students will follow up by completing the Post-Activity worksheet.
Example dolphin card:

1.
In a cove, there are a total of 200 dolphins. If 50 of these dolphins have rounded dorsal fins and 150 have pointed dorsal fins, what percentage of the population has rounded dorsal fins? What percentage of the population has pointed dorsal fins?
Rounded Pointed
2.
Dolphin skin color can either be dark gray or light gray. Using the terms,
dominant and recessive, explain why the calf of a dark gray dolphin (genotype
AA) and a light gray (genotype aa) dolphin is dark gray.

Name:______________________________
Punnett square:
In a cove, there are eleven adult male and eleven adult female bottlenose dolphins. There are also thirteen juvenile bottlenose dolphin calves. A disease, which is fatal to bottlenose dolphins is introduced to the population of dolphins living in the cove. The disease only affects dolphins with the recessive genotype, bb, while dolphins with dominant genotype,
BB or Bb, are immune to the disease. When 60% or more of dolphins in the population are
100
90
80
70
60
50
40
30
20 killed by the disease, the population cannot survive.
Use the class data from the chart on the next page to construct a bar graph below for the entire dolphin population.
10
BB or Bb
Genotype bb

What percent of the population has the recessive genotype, bb?
Will the population, as a whole, survive the disease? Why or why not?
Family Symbol Gender Age Class Genotype Probability of Calf
Genotype
Square
Square
Square
Circle
Circle
Circle
Diamond
Diamond
Diamond
Half Circle
Half Circle
Half Circle
Triangle
Triangle
Triangle
Crescent
Crescent
Crescent
Hexagon
Hexagon
Hexagon
Donut
Donut
Donut
Cylinder
Cylinder
Cylinder
Arrow
Arrow
Arrow
Arrow
Star
Star
Star
Star

30
20
10
0
70
60
50
40
BB or Bb bb
Genotypes
1.
Based on the above graph, what percent of the population a.
Has genotype BB or Bb? b.
Has genotype bb?
2.
If the 60% or more of the population has the recessive genotype, the population, as a whole, will not survive. Based on the recessive genotype percentage from the above graph, will the dolphin population, as a whole, survive the disease? Explain why or why not.