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Heredity, Genetics and Punnett Squares

Heredity, Genetics and Punnett Squares

Introduction: Heredity is the study of how traits get passed from parent to offspring. When scientists are evaluating how this happens, they use a tool called a Punnett square to determine the frequencies and probabilities that certain traits will be expressed in individual. For example, when two black-colored bears mate, the likelihood of their offspring having black fur is quite high. However, as a Punnett square can show, this is not always the case. It all depends upon the genetic conditions of the parents.

Gregor Mendel was an Austrian monk who was the first to study heredity in detail. He grew thousands of pea plants and manipulated which traits got passed on. It is from his work that science has a much more complete (although not entire) understanding of genetics. Gregor Mendel is deemed the "Father of Genetics."

Mendel discovered that some traits showed up more often than others. He called the traits dominant. In his experiments, Mendel crossed purple flowers with purple flowers and, no surprise, he got purple flowered offspring. However, then he crossed purple flowers with white flowers, he got purple flowers. What happened to the white? Well, when he then crossed the purple offspring from that first cross with each other, he got a combination of purple and white offspring. This led him to realize that the white trait was not gone, but was being masked by the purple. He called these traits recessive.

Directions for this Lesson: Answer the practice questions and then watch these videos to learn more about genetics and heredity.

Required Videos: