Mendelian genetics is one of the oldest and most fundamental fields of genetic research. It is named after Gregor Mendel, the Augustinian friar who discovered the basic principles of heredity in the early 19th century. His work laid the foundation for modern genetics and formed the cornerstone of the emerging field of molecular biology.
Mendel’s experiments were conducted on pea plants, which he selected because they were easy to grow and produce offspring quickly. He focused on seven traits that were easily observable, such as flower color, seed shape, and pod shape. By analyzing the offspring of different crosses, he was able to determine the basic rules governing inheritance.
One of the most important principles that Mendel discovered was the law of segregation. This law states that each individual has two factors (now called alleles) that determine a particular trait, one inherited from each parent. These factors can be either dominant or recessive. If an individual has two different alleles for a trait, one dominant and one recessive, only the dominant allele will be expressed in the phenotype.
When two individuals mate, each parent contributes one allele for each trait to their offspring. Therefore, each offspring has two alleles for each trait. When the alleles are different, one may be expressed over the other, depending on whether it is dominant or recessive. In other words, if an individual has one dominant allele and one recessive allele for a trait, the dominant allele will be expressed.
Mendel’s experiments demonstrated that when two individuals with different alleles for a trait mate, the resulting offspring have a 50/50 chance of inheriting either allele. This is known as the law of segregation. The alleles segregate during the formation of gametes, so that each gamete receives only one allele for each trait. When two gametes combine during fertilization, the resulting offspring again have two alleles for each trait, one inherited from each parent.
In summary, the law of segregation states that each individual has two alleles for each trait, one from each parent. The alleles segregate during gamete formation, so that each gamete receives only one allele for each trait. When two individuals with different alleles for a trait mate, the resulting offspring have a 50/50 chance of inheriting either allele. This basic principle forms the foundation of modern genetics and is essential for understanding the inheritance of traits in all organisms.
