Inheritance, Variation, Mendel's work on pea plants. PRINCIPLE OF INHERITANCE AND VARIATION

Inheritance, Variation, Mendel's work on pea plants. PRINCIPLE OF INHERITANCE AND VARIATION

Inheritance

It is the a process by which characters are passed on from parents to progeny.

Variation

It is the degree by which progeny differ from their parents.

Mendel’s Work on Pea Plants

Gregor Johann Mendel (father of genetics) worked on Pisum sativum pea plant for 7 years (1856-1863) and proposed the laws of inheritance.

·        Pea plants were selected for his experiments because-

1.     Pea has many distinct alternative traits (clear contrasting traits).

2.     Flower show self-pollination so, they are true-breeding plants.

3.     It is easy to artificially cross-pollinate the pea flowers.

·        Mendel select 7 characters in pea plants for carrying out his experiments.

Characters	Contrasting traits
	Dominant traits	Recessive traits
Seed shape	Round	Wrinkled
Seed color	Yellow	Green
Flower color	Violet	White
Pod shape	Full/Inflated	Constricted
Pod color	Green	Yellow
Flower position	Axial	Terminal
Stem height	Tall	Dwarf

·        Gene for seven characters present on 4 chromosomes-

Fig;1. Chromosomes in which genes for 7 characters present.

Learn More

• Phenotype is the physical appearance of an organism.

• The genotype is the genetic composition of an organism. It determines the phenotype of an organism.

• Mendel was born on July 22, in 1822

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• Mendel selected 14 true-breeding varieties for his experiments.

• Term ‘pure line’ was coined by Wilhelm Johannsen in 1903.

• True breeding organisms are also called purebred  is an organism that always passes down certain phenotypic traits to its offspring.

Summary

Inheritance is the process by which characters passed from parents to offspring and variation is the degree by which offspring differ from their parents. Mendel worked on pea plants for 7 years and proposed the laws of inheritance. Mendel selected 7 characters in pea plants for his experiments, they are seed shape, seed color, pod shape, pod color, flower shape, flower color, flower position, and stem height.