Mendel and Basic Heredity


  1. Recognize how a scientist’s identity and experience affect their science.
  2. Define gene, allele, locus, genotype, phenotype, dominant, recessive, monohybrid, dihybrid. Compare and contrast a testcross, a monohybrid cross, a dihybrid cross.
  3. Define the law of Equal Segregation and explain how it is illustrated in the progeny of a cross between a homozygous recessive (aa) and heterozygous (Aa) individual.
  4. Define the law of Independent Assortment and explain how it is illustrated in the progeny of a dihybrid cross (AaBb x AaBb) or a dihybrid testcross (AABB x AAbb).
  5. Use a Punnett square to predict potential offspring from a given cross.
  6. Use the Addition Rule and Multiplication Rule of probability to predict the likelihood of an outcome.

What makes you, you?

What do you look like? Do you have brown eyes or green eyes? Are you tall, short, or medium height, and do you have light skin or dark skin?

How do you behave?  Do you run fast or are you very flexible? Do you have perfect pitch? Are you a thrill-seeker, or do you prefer more relaxing activities?

These types of measurable traits – whether they are easily visible, like physical attributes, or other measurable characteristics, like behavior or aptitude for a skill – make up your phenotype. The traits listed above all are likely to have an underlying genetic cause: a small variation in a part of your DNA (a gene or a locus), compared to other people, that may predispose you to a certain appearance or behavior. These different versions of a gene are called alleles, and your particular combination of alleles is called your genotype.

Classical genetics, transmission genetics, and Mendelian genetics are three terms that all refer to the same thing: genetic research that relies on tracking traits from parent to offspring. Classical genetic experiments compare the phenotypes of parents and offspring to infer their genotype. Studying how traits are passed from one generation to the next was historically the earliest type of genetic research, beginning with the work of Gregor Mendel in the mid-1800’s.

This module gives a brief biography of Gregor Mendel and his contribution to the field of genetics, including the laws of equal segregation and independent assortment. You’ll practice using Punnett squares and the addition and multiplication rules of probability.


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