Mendelian inheritance
Introduction
Mendelian inheritance, also known as Mendelian genetics, is a type of biological inheritance that follows the laws originally proposed by Gregor Mendel in 1865 and 1866 and re-discovered in 1900. These laws were initially controversial. When Mendel's theories were integrated with the Boveri–Sutton chromosome theory of inheritance by Thomas Hunt Morgan in 1915, they became the core of classical genetics.
Mendel's Experiments
Mendel performed his experiments on pea plants (Pisum sativum) because they possessed four important qualities: they were available in many varieties, they could be grown easily and quickly, they had observable traits with variations, and they could self-fertilize or be cross-fertilized.
Principles of Mendelian Inheritance
Mendelian inheritance is characterized by three principles: the principle of segregation, the principle of independent assortment, and the principle of dominance.
Principle of Segregation
The principle of segregation, also known as the law of segregation, states that every individual organism contains two alleles for each trait, and that these alleles segregate (separate) during meiosis such that each gamete contains only one of the alleles.
Principle of Independent Assortment
The principle of independent assortment, also known as the law of independent assortment, states that genes for different traits assort independently of one another in the formation of gametes.
Principle of Dominance
The principle of dominance, also known as the law of dominance, states that in a heterozygote, one trait will conceal the presence of another trait for the same characteristic. Rather than both alleles contributing to a phenotype, the dominant allele will be expressed exclusively.
Extensions to Mendel's Laws
While Mendel's laws provide a comprehensive framework for understanding the basics of genetics, they do not explain all observations of heredity. For instance, they do not account for the phenomenon of genetic linkage, the existence of multiple alleles, gene interactions, or non-nuclear inheritance.
Modern Applications of Mendelian Genetics
Mendelian genetics continues to be a fundamental principle in the field of genetics, with applications in disease research, agriculture, and biotechnology.