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Key Ideas

  • Pedigrees are important tools for geneticists to use in tracing traits and variations from one generation to the next.
  • Genes have different forms, called alleles. Two alleles make up a gene pair for a specific trait.
  • A dominant allele expresses its trait whenever it is present in a gene pair. Two recessive alleles must be present in order to express that trait.
  • Gregor Mendel's work studying inheritance in garden peas in the 1860s laid the foundation for the modern science of genetics.


Students apply principles of heredity to create and study family pedigrees. They analyze information about family members and investigate inheritance of particular traits, such as hair and eye color. They learn to use a Punnett square, an important tool of geneticists, to predict offspring from genetic crosses involving dogs that have different coat colors. Students use colored beans to model and explain the differences in inheritance patterns of dominant and recessive alleles. After reviewing Gregor Mendel's work studying inheritance patterns of garden peas, students apply their knowledge to explain how research on chromosomes and genes can now be used to verify and extend the work of Mendel, whose data dates back to the 1860s.



explain the biological significance of gene alleles.

explain how variations are inherited.

examine pedigrees and explain inherited variations.

demonstrate how to use a Punnett square to predict outcomes of crosses between dogs having different coat colors.

model differences in the expression of dominant and recessive alleles.

explain how Gregor Mendel's explanations for variations in garden peas can be verified using modern biological research on genes, alleles, and chromosomes.


alleles, dominant allele, genotype, heredity, linked genes, pedigree, recessive allele

Student Materials

Activity 6-1 Expression: Dominant and Recessive

  • Activity Report
  • 20 white beans; 20 red beans; 2 jars or cups; Paper and pen/pencil

Teacher Materials

Activity 6-1 Expression: Dominant and Recessive

  • Activity Report Answer Key

Advance Preparation

See Activity 6-1 in the student edition

Activity 6-1 Expression: Dominant and Recessive

  • Obtain red and white beans and place 10 of each color in a separate cup.
  • Gather one set of student materials for each group of students.
  • Have extra red and white beans available.
  • Coordinate this interdisciplinary activity with the math teacher.

Interdisciplinary Connections

Math Complete activities relating to probability, using percentages and fractions.

Social Studies Examine a pedigree chart for the Russian Czar Nicholas and his wife Alexandra showing the members of the royal family and the pattern of inheritance of hemophilia.

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6 , 7 , 8

Date Created:

Feb 23, 2012

Last Modified:

Apr 29, 2014
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