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6th Grade Science / Lesson 4 - Heredity

Heredity
What will we be learning today?


  • In this lesson, we are going to learn all about the study of heredity.


  • People have always noticed that offspring inherit many traits from their parents, but the way heredity works was not very well understood until about 100 years ago. The scientific study of heredity began in the 19th century, when an Austrian monk named Gregor Mendel carried out experiments with different varieties of garden peas.

  • Mendel grew up on his family's farm. As he learned how to care for plants and animals, he became curious about how traits are passed from one generation to the next. He wondered why all brothers and sisters don't look alike.


After studying science and math in school and at a university, he became both a priest and a science teacher. In 1857 Mendel was put in charge of the gardens at the monastery where he lived.

 

Gregor Mendel (1822-1884) was the first person to count the numbers and types of offspring of pea plants to measure the inheritance of specific traits. He is now considered the father of genetics.


He began conducting carefully controlled experiments to trace how certain traits were passed from parent pea plants to their offspring. Mendel studied the same kind of peas you've probably eaten. Pea plants have distinct traits, which are easy to trace from one generation to another. Peas' offspring grow and mature quickly, so Mendel was able to conduct many experiments and gather large amounts of scientific data. Mendel used scientific methods, kept detailed records, and analyzed his data mathematically. After eight years he presented his findings to the National Science Society in Austria.


Mendel wrote descriptions of his research in a scientific paper that was published in 1866. Scientists of that time did not pay much attention to Mendel's results. Years later, around the year 1900, three other scientists who had reached conclusions very similar to Mendel's rediscovered his published papers. These scientists recognized the value of Mendel's work. In 1909 the study of how heredity works became known as genetics. Since then Gregor Mendel has been called the father of genetics.


  • Mendel found that each tall offspring in the first generation carried both tall and short traits. He called tallness the dominant trait. He called shortness the recessive trait. A dominant trait is the form of the trait that appears in the offspring generation. A recessive trait is the form of a trait hidden, or masked, in the offspring generation.

  • Every time Mendel crossed two offspring, he got the same result. For every three offspring that showed the dominant trait, one showed the recessive trait. There was always a ratio of three dominant to one recessive, or 3:1. A ratio is a mathematical term that describes the relationship between two quantities. You can also write the ratio 3:1 as "3 to 1" or as 3/1 .


  • Let's Review What We Learned Today!


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    • Then complete your worksheet!