Heredity and Mendel’s Three Principles

By Staff WriterLast Updated May 27, 2020 7:30:54 PM ET
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Who would have thought that an Austrian monk would become the “father of modern genetics?” Gregor Mendel was a monk and a master gardener who found inspiration in his pea plants. In the end, he discovered that traits in those plants followed specific patterns. From there, he nurtured three theories that laid the foundation for the study of genetics and heredity.

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If you’ve ever wondered why you have your dad’s curly hair and your mom’s blue eyes, you could thank Gregor Mendel for modern science’s explanation. He discovered why certain traits get passed down every generation while others skip. His findings made it possible for scientists to better understand how humans inherit characteristics and traits.


The Science of Studying Inheritance


The traits and characteristics that get handed down from generation to generation are encoded human genes. Genes can be found in the nucleus of every cell. They're made from strands of DNA. Genes add specific proteins to create, maintain, and regulate the body. They help control everything from building bones to keeping a constant heart beat. The study of genes and the way that traits are inherited is called genetics, according to the

National Institute of Science.

In modern science, researchers and scientists can study genetics to help improve the way conditions are diagnosed, treated, and prevented. All of that might not be possible without Gregor Mendel’s contribution to the world. 


Who was Gregor Mendel?


Born in Austria in 1822, Gregor Johann Mendel's early life was spent in a quiet, rural setting. He lived on his family's farm until he was 11 years old. Then, a teacher recommended to his family that he be sent to secondary school. He graduated with honors and went on to study math and physics at the Philosophical Institute at the University of Olmutz. Instead of taking his father's place in running the family farm, Mendel decided to become a monk, and entered the Augustinian order and took the name Gregor. Later, he continued his scientific studies at the University of Vienna.


After graduating, he returned to the monastery and took a teaching position.

Biography notes that he began researching heredity characteristics in plants in 1854.

Mendel’s Three Principles


So why peas? The popular legume had numerous varieties, and were fast and easy to produce (and reproduce). That's why Mendel used these plants for his experiments.


Cells duplicate their DNA to produce reproductive cells. The process is called "meiosis." Mendel found that most cells have two copies of each chromosome. After going through meiosis, the reproductive cells have one copy of the chromosomes. Then, during reproduction, two reproductive cells join and form cells that once again have two chromosomes. This new cell is called a zygote. It has a copy of each chromosome from each of the parents. How the new individual looks depends on whether it inherits dominant or recessive copies of chromosomes.


From 1854 to 1863, Mendel conducted experiments on tens of thousands of plants. His work led him to identify three laws of heredity.


Principle of Dominance


Dominant traits are those that always get passed down to offspring. Mendel found that whenever he crossed tall pea plants with genotype TT and short pea plants with genotype tt, all of the offspring had a genotype of Tt, yet always presented as tall. This, he realized, is because the dominant trait always suppresses the recessive trait. 


Principle of Segregation


This was one of Mendel's first conclusions during his experiments. He found that some dominant and recessive traits were passed randomly from parent to child. Mendel found that parents could have two different forms of a gene—one of each copy of a chromosome. This theory states that these forms are separated during meiosis.


Principle of Independent Assortment


The last of Mendel's principles is the law of independent assortment. This principle states that traits inherited through a gene are inherited independently from the traits inherited through other genes.