What is Mendel and Inheritance? | Types, Definition, Structure, Function & Facts
What is Heredity?
Heredity is when certain traits are passed from parents to children. Traits are traits such as eye color, height, and athletic ability. Heredity is transmitted through the genes of the DNA molecule. In biology, the study of heredity is called genetics.
Gregor Mendel
Gregor Mendel (1822-1884) is considered the father of genetics. Through testing, he discovered that certain traits are inherited in specific patterns.
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Gregor studied inheritance by experimenting with peas in his garden. Peas are an excellent test subject because they can self-pollinate and fertilize and have many traits that only come in two forms. This allowed Mendel to easily control his experiments and reduce the likelihood of outcomes to something he could record and manage.
Mendel’s Experiments
Gregor studied seven characteristics of pea plants: seed color, seed shape, flower position, flower color, fruit shape, pod color, and stem length. Mendel’s experiments took place in three main stages:
1. He created the first generation of purebred plant parents. He created them by letting the plants self-pollinate until he learned that they reproduced faithfully with seven traits. For example, plants with purple flowers always produce seeds with purple flowers. He called these plants generation P (for parents).
2. He then created a second generation of plants (F1) by selecting two different purebred P plants.
3. Then he created the third generation of plants (F2) by self-pollinating two plants from the F1 generation with similar characteristics.
Mendel’s Experiment Results
Mendel found surprising results from his experiments.
F1 Generation
Mendel discovered that the F1 generation all produced similar traits. Although both parents have different characteristics, the children still have similar characteristics. For example, if he crosses a P plant with purple flowers with a P plant with white flowers, all of the progeny plants (F1) will have purple flowers. Because purple flowers are dominant.
These results can be represented in a diagram called a Punnett square. Dominant genes are indicated in capital letters and recessive genes in lowercase letters. Here, purple is the dominant gene denoted by the letter “P” and white is the recessive gene represented by the letter “w”.
| P | P | |
| w | Pw | Pw |
| w | Pw | Pw |
F2 Generation
Here’s a Punnett square showing that 25% of offspring have two “w” genes that cause them to have white flowers:
| P | w | |
| P | PP | Pw |
| w | Pw | ww |
Homozygous and Heterozygous
When two of the genes are identical (as with “PP” or “ww” above), they are said to be homozygous. When they are different (as with “Pw”) they are said to be heterozygous.
Interesting Facts about Mendel and Inheritance
Mendel’s work was rejected by fellow scientists during his lifetime. Only then was his work rediscovered and confirmed by new experiments.
Mendel was a monk and performed his experiments in the monastery’s garden. His trial was largely over when he was promoted to abbot.
Mendel also conducted experiments with honey bees, but found them much more difficult to experiment with.
The idea that children receive one unit of inheritance from each parent is called “segregation theory”.