Mendelian Genetics

Mendelian genetics revolves around the principles put forth by Gregor Mendel, a 19th-century monk who conducted extensive research on pea plants. It deals with the inheritance of traits from parents to offspring.
Gregor Mendel is often referred to as the “father of genetics”. Through his work, he discovered the fundamental laws of inheritance.

Mendel performed thousands of cross-breeding experiments using pea plants. He focused on seven traits: seed shape, seed colour, flower colour, flower location, pod shape, pod colour, and plant height.
Through meticulous record-keeping of the traits exhibited in the offspring he bred, Mendel came up with two principles: the law of segregation and the law of independent assortment.

The law of segregation states that an individual inherits a unit of genes for each trait from each parent. These units, termed alleles, can be dominant or recessive.
In the formation of gametes, the two alleles for each trait segregate (separate) from each other. Therefore, each gamete carries only one allele for each trait.
Dominant alleles mask recessive ones; hence, the dominant trait appears in the offspring if at least one dominant allele is present.

According to the law of independent assortment, the alleles of two (or more) different traits are distributed to gametes independently of each other. In simpler terms, the inheritance of an allele for one trait does not affect the inheritance of an allele for another trait.
This creates more variation because different combinations of traits can occur in the offspring.

Punnett squares are graphical tools used in genetics to predict the probability of possible genotypes and phenotypes in the offspring resulting from a cross between parents with known genotypes.
Through Punnett squares, complex genetic traits and inheritance probabilities can be simplified for easier understanding.

Not all traits follow Mendel’s laws of segregation and independent assortment. Exceptions include characteristics influenced by multiple genes, or those affected by conditions outside genetics, such as incomplete dominance, codominance, and polygenic inheritance.