Inheritance patterns from graphs and charts

Course Outline

     I Interpreting inheritance patterns

        A.  Using Graphs and Charts

              1.  Pedigrees                  

                  a. Analyzing Pedigrees                     

                     1)  Infering genotypes

                      2)  Predicting disorders

         B.  Bar graphs

Teaching Aids

1.  Computer

2.  Smart Board

3.  Power point

4.  Worksheet

 Height (tallness) in humans is polygenic but the mechanism of gene function or the number of genes involved is unknown.Suppose that there are 3 loci with 2 alleles per locus (A, a, B, b, C, c).Assume that:Each active allele (upper case letters: A, B, or C) adds 3 inches of height.The effect of each active allele is equal, A = B = C.Males (aabbcc) are 5' tall. Females (aabbcc) are 4'7".


Aabbcc (or aaBbcc etc.)5'3"4'10"
AaBbcc etc.5'6"5'1"
AaBbCc etc.5'9"5'4"
AaBbCC etc.6'0"5'7"
AaBBCC etc.6'3"5'10"
The following is a cross between two people of intermediate height.AaBbCc X AaBbCcIf there is independent assortment, the following gametes will be produced in equal numbers:ABC, ABc, AbC, aBC, abC, aBc, Abc, abcPunnett square analysis:The Punnett square above can be summarized as follows:


AaBBCC etc.6'3"5'10"6/64
AaBbCC etc.6'0"5'7"15/64
AaBbCc etc.5'9"5'4"20/64
AaBbcc etc.5'6"5'1"15/64
Aabbcc etc.5'3"4'10"6/64

Assignment:  The frequency column in the table above can be plotted to produce a graph.  After the graph is completed write a short paragraph describing what the graph tells you about the trait.

5.  After a lesson on pedigrees students are assigned the task of loggin on to this website  They must answer the questions and turn them in.  Previous instructions have provided them with the knowledge to complete this task

Class Projects

Investigate Human Pedigrees

Where are the branches on the family tree?  Unlike some organisms, humans reproduce slowly and produce a few offspring at one time.  One method used to study human traits is pedigree analysis.


1.  Read and complete the lab safety form

2.  Imagine that you are a geneticist interviewing a person about his or her family concerning the hypothetical trait of hairy earlobes.

3.  From the transcript below, construct a pedigree.  Use appropriate symbols and format. 

"My name is Scott.  My great grandfather Walter had hairy earlobes(HEs), but great grandma Elsie did not.  Walter and Elsie had three children:  Lola, Leo, and Duane.  Leo, the oldest, has HEs, as does the middle child Lola: but the youngest child, Duane, does not.  Duane never married and has no children.  Leo married Bertie, and they have one daughter, Patty.  In Leo's family, he is the only one with HEs.  Lola married John, and they have two children:  Carolina and Luetta.  John does not have HEs, but both of his daughters do."


1.  Assess -In what ways do pedigrees simplify the analysis of inheritance?

2.  Think Critically - Using this lab as a frame of reference, how can we put to practical use our understanding of constructing and analyzing human pedigrees?

Bar Graph Assignment

Use a Bar graph to determine which genetic disorder is more prevalent in the United States.  Collect data for the following diseases:  sickle cell anemia, cystic fibrosis, neurofibromatosis, hemophilia, Down syndrome, Kleinfelter syndrome and Duchenne muscular dystrophy.  Please provide this information on a poster board.

Review Questions

1.  A ____________ is a visual display used to compare the amounts or frequency of occurrence of different characteristics of data.

2.  A bar graph display allows us to compare groups of data and to make generalizations about the data quickly.

      _______True                __________False

3.  How is the inheritance pattern between parents and offspring represented diagrammatically?

4.  Draw the symbols for normal female, normal male, female who expresses the trait being studied, male who expresses the trait being studied, female who is a carrier for the particular trait, male who is a carrier for the particular trait, generation, parents, siblings, generations, individuals in a certain generation.

5.  A pedigree is a quick way to see all the genotypes and phenotypes in an entire family.

      _______True              ________False 

6.  A male with diabetes would be represented by a half filled circle.

     _______True               ________False


Sometimes students get a clearer understanding by reading different sources for information.  They may try this link to learn more about genetics.

Other Useful Information

Students will visit the following website and construct a pedigree for one trait.