Difference between Dominant and Recessive Traits

When we hear the word traits, we think of the distinguishing characteristics of people. We know that a child doesn’t necessarily look like his/her parents but would have their features. This essentially means that traits like the color of the eyes, hair, skin, etc. are determined by genes that are inherited from the parents. Each parent contributes equally for the expression of a particular trait. When the alleles are dominant then the trait is expressed but if some traits are absent or not expressed in the child but the allele is present in the parent then it is called a recessive trait. 

Gregor Johann Mendel, widely known as the ‘Father of Genetics’, conducted hybrid experiments on garden peas and published the results in the year 1860, thereby laying the foundation of genetics. He proposed three laws known as ‘Mendel's laws of Inheritance’. The experiments proved that the dominant allele can be determined by observing the phenotypic traits in the offspring but the recessive allele that remains hidden can be passed to the offspring and expressed in later generations.

History of Inheritance

• The expression of a particular trait is determined by the presence of two alleles contributed by the father and the mother.
• In such a case, the expression of a particular trait is determined by Mendel’s principles of inheritance.
• Gregor Johann Mendel (1822- 1884) used garden peas to study the expression of visible traits.
• He crossed pea plants with characteristic tall/short and round/wrinkled seeds and studied the progenies.
• He observed that there were no mixed characteristics in F1 progeny when he crossed a tall plant (TT) with a short plant (tt), i.e.; there were no medium-heightened plants; instead all the F1 progeny were tall plants.
• By self-pollinating the progeny plants, he found that one-fourth of the F2 generation was short and hence he formed the laws of inheritance.

Principles of Inheritance by Mendel

Mendel laid the foundation of genetics and proposed the principles which state that the traits are passed from one generation to another and sometimes, they even skip generations. A central conclusion drawn from Mendel’s experiment was that the internal nature of an organism cannot be simply determined by external resemblance. Scientists use ‘phenotype’ for external resemblance and ‘genotype’ for internal resemblance. So, to quote this in scientific terms; an organism’s genotype cannot be determined by observing the phenotype. Certain recessive phenotypes could skip generations to re-emerge in later generations.

How do genes pass from one generation to the next?

The gene responsible for a specific trait comes in different allelic forms. When both the parents pass on the same allele for the gene then the offspring is called homozygous for that specific trait. If both the parents pass on different alleles for the trait then the offspring is called heterozygous for the trait. Alleles are responsible for phenotypes (the physical expression of a particular trait) that could be dominant or recessive. The phenotype of traits is due to masking which results in the expression of dominant allele over recessive.

Difference between Dominant and Recessive traits

Mechanism of Trait Expression

• Cellular DNA is responsible for making the proteins in the cell.
• A particular gene is related to the efficient formation of a particular protein in the cell.
• If the genes function efficiently then a huge amount of proteins are made whereas if the genes are inefficient, fewer proteins are made.
• Each gene set is present as independent copies as chromosomes and thus each gene has two copies of chromosomes in the cell.
• When germ cells are formed they carry one copy of chromosome from either parent, male and female.
• When two germ cells are combined in the offspring then they restore the normal set of genes in the individual which ensures the stability of the DNA of the species.
• Such a mechanism explains Mendel’s laws of inheritance in all sexually reproducing organisms.

Things to remember

• Traits are the phenotypic characters expressed in an individual which are determined by the dominant alleles.
• Alleles are the genetic characters that determine the expression of traits in an individual.
• Gregor Johann Mendel proposed laws of inheritance through his experiments with garden peas.
• The presence of a single dominant allele results in the expression of a particular trait whereas the presence of two recessive alleles results in the expression of recessive character in an individual.
• Each parent contributes a single allele to the offspring and the combination of both the alleles from either parent results in the expression of that particular trait in the offspring.