The field of science that examines how genes and genetic traits are inherited from one generation to the other is known as genetics. Mendelian genetics is the study of the physical traits of individuals. These are also known as phenotypes.

Gregor Mendel was a 19th-century Augustinian monk and the humble founder of genetics. From 1856 up till 1863, Gregor Mendel tested 28,000 pea plants. From his observations, he deduced two theories. These are now called Mendel's Laws of Inheritance or Mendelian Inheritance. Mendel described these two laws in a paper called "Experiments on Plant Hybridization", published in 1866.

Read on to learn more about the Gregor Johann Mendel experiment.

Mendel’s Laws of Inheritance

Mendel crossed a true-breeding white flower and a purple flower plant. To his astonishment, he discovered that the product was a purple flower instead of a combination of two colours. He then deduced the idea of "factors" or hereditary units. Of these, one was recessive and the other dominant. Moreover, Mendel stated that these factors, which we now call genes, always occur in pairs.

Mendel then self-fertilised the F1 generation, and in the F2 generation, he observed that the flowers showed phenotypes in the ratio 3:1. Thus, he theorised that genes or these factors could be paired in three combinations: AA, Aa and aa. The capital A stands for the dominant trait while the lowercase a stands for the recessive trait.

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The Gregor Johann Mendel Experiment

Gregor Mendel now decided to analyse the patterns of inheritance in the pea plant. He picked out the pea plant due to the following reasons:

Peas are self-pollinating. They can also be self-pollinated.
Peas are annual plants. Thus, many generations of this plant can be examined in a very short span of time.
Pea plants have a set of 7 distinct character traits.
Peas are easy to grow.

After that, Mendel began to observe a pair of contrasting traits at a time, and he experimented using true-breeding pea plants. These were the characteristics that he studied.

How well have you learnt about Mendel’s experiments? Test yourself with this quiz.

Pop Quiz 1

Which of these is a trait Mendel studied in the pea plant?

Leaf shape
Leaf colour
Flower shape
Seed shape

Mendel made sure to use only true-breeding plants in his experiments. True-breeding plants exhibit stable inheritance of traits. Subsequently, in each of his experiments, Mendel noticed a pattern of traits and inheritance. These laid the foundation of his laws of inheritance.

Read on to find out more about the results of the Mendel experiment (class 10).

Results of Gregor Mendel’s Experiments

The following were the observed results of his experiments with the pea plant.

Firstly, Mendel took note that all plants in the F1 generation were tall and there were no dwarf plants.
Secondly, in the F2 generation, Mendel made the observation that pea plants were tall, while one was a dwarf plant.
Consequently, Mendel observed that the same results were seen for other characters as well.
In the F1 generation, these traits of only one parent came to the fore. Meanwhile, in the F2 generation, these traits of the other parent plant also came to the fore.
The traits that appeared in F1 are now known as dominant traits, whereas the ones that appeared in the F2 generation are known as recessive traits.

To sum it up, the genes which were passed from one generation to the others were existing in pairs called alleles. Two similar alleles are known as homozygous alleles. Different alleles are called heterozygous alleles.

Test what you know with the following quiz.

Pop Quiz 2

A heterozygous yellow pea plant has the following alleles.

Finally, Mendel's observations led to the three primary Laws of Inheritance.

Law of Dominance
The Law of Segregation
Law of Independent Assortment.

For more on Mendel experiment class 10 and the laws of inheritance, check out our detailed study material. Now you can also download our Vedantu app for easier access to our detailed notes, as well as online interactive sessions for doubt clearing.

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FAQs on Mendel’s Law of Inheritance: Key Experiments and Results

1. What are the key reasons Gregor Mendel chose the pea plant (Pisum sativum) for his inheritance experiments?

Mendel selected the pea plant for his experiments due to several advantageous characteristics that made it an ideal model organism. These include:

Short Life Cycle: Pea plants are annuals, allowing Mendel to study multiple generations in a relatively short period.
Contrasting Traits: The plants exhibited several easily distinguishable, contrasting traits (e.g., tall vs. dwarf, round vs. wrinkled seeds).
Self-Pollination: Pea flowers are naturally self-pollinating, which ensures pure-line traits can be maintained.
Controlled Cross-Pollination: Emasculation (removing the anthers) and manual pollination allowed Mendel to perform controlled crosses between different parent plants.

2. What were the seven pairs of contrasting traits in pea plants that Mendel studied in his experiments?

Mendel meticulously observed seven pairs of contrasting characters in his pea plant experiments. Each character had two distinct forms, one dominant and one recessive:

Stem Height: Tall (dominant) vs. Dwarf (recessive)
Flower Colour: Violet (dominant) vs. White (recessive)
Flower Position: Axial (dominant) vs. Terminal (recessive)
Pod Shape: Inflated (dominant) vs. Constricted (recessive)
Pod Colour: Green (dominant) vs. Yellow (recessive)
Seed Shape: Round (dominant) vs. Wrinkled (recessive)
Seed Colour: Yellow (dominant) vs. Green (recessive)

3. How did Mendel's monohybrid cross experiment demonstrate the principles of dominance and segregation?

A monohybrid cross involves tracking a single character. When Mendel crossed a pure-line tall plant (TT) with a pure-line dwarf plant (tt), he observed:

F1 Generation: All offspring were tall. This demonstrated the Principle of Dominance, where the allele for tallness (T) masked the effect of the allele for dwarfness (t).
F2 Generation: Upon self-pollinating the F1 plants, the offspring appeared in a ratio of approximately 3 tall to 1 dwarf. The reappearance of the dwarf trait showed that the recessive allele (t) was not lost but had separated, or segregated, from the dominant allele (T) during gamete formation. This formed the basis of the Law of Segregation.

4. Why is the reappearance of the recessive trait in the F2 generation a crucial observation in Mendel's experiments?

The reappearance of the recessive trait in the F2 generation is fundamentally important because it disproved the prevailing theory of 'blending inheritance.' It demonstrated that hereditary units (now called genes) are discrete particles that retain their identity from one generation to the next. The recessive trait's reappearance showed that its corresponding factor was only masked in the F1 generation, not destroyed or blended, proving that heritable factors segregate during gamete formation.

5. What is a dihybrid cross, and how did it lead Mendel to formulate the Law of Independent Assortment?

A dihybrid cross is an experiment that tracks the inheritance of two different characters simultaneously, such as seed shape and seed colour. When Mendel crossed a plant with round yellow seeds (RRYY) with one having wrinkled green seeds (rryy), the F2 generation produced a phenotypic ratio of 9:3:3:1. The appearance of new combinations (round-green and wrinkled-yellow) showed that the alleles for seed shape assorted into gametes independently of the alleles for seed colour. This observation is the foundation of Mendel's Law of Independent Assortment.

6. What is the fundamental difference between the Law of Segregation and the Law of Independent Assortment?

The fundamental difference lies in the number of genes they describe. The Law of Segregation applies to a single gene, stating that its two alleles separate from each other during the formation of gametes, so each gamete receives only one allele. In contrast, the Law of Independent Assortment applies to two or more different genes, stating that the alleles for one gene segregate independently of the alleles for another gene during gamete formation. In essence, segregation describes the behaviour of alleles for one trait, while independent assortment describes how different traits are inherited relative to one another.

7. What is the importance and application of a test cross in Mendelian genetics?

A test cross is a diagnostic tool used to determine the genotype of an organism that displays a dominant phenotype. Since an organism showing a dominant trait could be either homozygous dominant (e.g., TT) or heterozygous (e.g., Tt), a test cross clarifies this. It is performed by crossing the individual with the unknown genotype with an individual that is homozygous recessive (e.g., tt) for the trait. The resulting offspring ratios reveal the parent's genotype, which is a practical application of Mendel's experimental logic.

8. Why were the results of Mendel's experiments not widely recognised by the scientific community during his lifetime?

Mendel's groundbreaking work on inheritance went largely unnoticed for over three decades for several reasons:

Lack of Communication: Scientific communication channels were limited, and his work was published in a relatively obscure journal.
Novel Approach: His use of mathematics and statistics to explain biological phenomena was a new and unfamiliar concept for most biologists of his time.
No Physical Proof: Mendel proposed the existence of 'factors' (genes) as discrete units, but he could not provide physical evidence for their existence, as concepts of chromosomes and meiosis were not yet established.