Gregor Johann Mendel was a pioneer among geneticists who put forward the concept of inheritance of characteristics or traits from parent to offspring. Mendel proposed the principle of inheritance and is known as the “Father of Genetics”. Mendel has chosen pea plants for his experimentation and found variations among them. Gene is a structural and functional unit of heredity and variations. Gene is a DNA segment on the chromosome. Genes control the expression of characteristics. Mendel called the genes to be factors.
Traits can be either dominant or recessive. Tallness in a plant is a dominant trait, controlled by a dominant allele and is represented by “T” (capital). Shortness in a plant is a recessive trait, controlled by a recessive allele and is represented by “t” (small).
• Homozygous is a condition in which a gene possesses a pair of the same alleles (TT or tt) for a single characteristic.
• Heterozygous is a condition in which a gene possesses a pair of different alleles (Tt) for a single characteristic.
Phenotype is a morphological expression of a single character. For example, tallness or shortness represents the phenotype of the plant. Genotype is the genetic make-up of a cell, an organism, or an individual (i.e. the specific allele make-up of the individual), usually with reference to a specific characteristic under consideration. Alleles combine to make a genotype, such as TT or Tt or tt.
Punnett square is a statistical method that was used by Mendel to predict the possible genotypes and phenotypes of the offspring.