Mendel's experiment

Inheritance and Heredity

 

Mendel’s Law of Inheritance for Class 5 Science

 

From this concept, the students will learn about Mendel’s Law of Inheritance and how the traits of different physical characters are passed on from one generation to another generation.

After reading the concept, students will be able to:

• Know about Mendel’s experiment with pea plants.
• Understand how do Mendel’s experiment show that traits are inherited independently.
• Know what is a gene and different types of inherited traits like eye colour, curly hair, rolled tongue etc.
• Understand what is a dominant gene and recessive gene.
• Know about different laws proved by Gregor Johan Mendel such as
• Mendel’s first law or Mendel’s law of dominance.
• Mendel’s second law or Mendel’s law of segregation.
• Mendel’s third law or Mendel’s law of independent assortment.
• Recall 7 characteristics of pea plants by Gregor Mendel.

Each concept is explained to class 5 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

Download the worksheets and check your answers with the worksheet solutions for the concept of Mendel’s Law of Inheritance provided in PDF format.

 

What Is a Gene?

Traits are the characters we have in our bodies. We inherit these traits from our parents. But what leads to this transmission of traits?

 

Expression of Inherited Traits:

• Genes have a particular function to perform.
• Genes are made up of DNA or deoxyribonucleic acid.
• Every gene is responsible for the synthesis of one particular type of protein.
• Now, protein plays a vital role in almost every function of our bodies.
• The synthesis of proteins from the genes is responsible for the development of traits in our bodies.
• The type of genes we have thus decide the type of our hair, skin, height, facial features etc.
• We get genes from both our parents, half from our mother and half from our father.

 

What Will Happen If Only Half of the Genes Are Not Inherited From the Parents?

 

How Are Traits Expressed?

 

Dominant and Recessive Genes:

Let us see the dominant and recessive genes in the following family.

• Both father and mother are tall, i.e. they have the dominant gene.
• The child who inherits the dominant gene from a parent is tall.
• However, the child who does not inherit the dominant gene is short.

 

Gregor Mendel—The Father of Genetics:

• The branch of science that deals with studying genes and their inheritance is called genetics.
• Gregor Mendel is considered the Father of Genetics for his work on genes.
• He was born in 1822 in a poor family in Austria.
• Through his work on pea plants, he discovered the laws of inheritance.
• In his work, he stated that genes occur in pairs. People did not understand his conclusions at that time. His work was restudied after his death.

 

Why Did Mendel Choose the Pea Plant for His Experiment?

• The pea plant showed various contrasting factors, either dominant or recessive.
• There was no scenario where a trait intermediate between dominant and recessive was expressed.
• A pea plant is easy to grow and maintain.
• It made the experiments be conducted efficiently without any complex results.
• Mendel grew around 10,000 pea plants and kept track of the progenies.
• He recognised mathematical patterns of inheritance from generation to generation, which you will study in detail in higher classes.

He concluded the following things after his experiments—

1. Law of segregation: It stated that each inherited trait is controlled by a pair of genes. These genes are randomly segregated in the cells of parents during the formation of gametes.
2. Law of Independent Assortment: The genes of different traits are not affected by each other. They are inherited independently by the next generations.
3. Law of Dominance: A recessive gene would not affect the expression of a trait in the presence of the dominant gene. A dominant gene would express itself even if the recessive gene is present.

 

Now let us understand the laws on inheritance with examples:

• In the previously stated example, both the genes for tall and short were inherited by the siblings. It validates the law of segregation and independent assortment.
• The tall child may have inherited the gene for short height, but he is tall because he inherited one dominant gene for tallness. It validates the law of dominance.

 

Contrasting Traits of the Pea Plant:

 

 New Words

 

Did You Know?