Mendelian Genetics: Definition, Overview, Synonyms, Examples, Process, Factors, Topics

Mendelian genetics is the study of how traits are inherited from one generation to the next, based on the principles discovered by Gregor Mendel. Through his experiments with pea plants, Mendel identified key laws of inheritance, such as the Law of Segregation and the Law of Independent Assortment. These principles explain how dominant and recessive alleles determine traits in offspring. In this article, mendelian genetics, Mendel’s experiments, mendelian traits and terminology, mendelian crosses, and applications of mendelian genetics are discussed. Mendelian Genetics is a topic of the chapter Principles of Inheritance in Biology.

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This Story also Contains

1. What are Mendelian Genetics?
2. Mendel’s Experiments
3. Mendel's Laws of Inheritance
4. Mendelian Traits and Terminology
5. Mendelian Crosses
6. Applications of Mendelian Genetics

What are Mendelian Genetics?

Mendelian genetics is the study of genes and their attributes as they are passed from one generation to another. It gets its name from Gregor Mendel. The science of genetics provides support for classical genetics and is very instrumental in helping to unlock how the mechanics of inheritance work. Mendelian inheritance cannot be compromised when studying biology, simply because it explains how these features are transmitted from one generation to another and how variation is brought into a population.

Gregor Mendel, an Austrian monk, conducted groundbreaking experiments in the 19th century that contributed tremendously to knowledge about heredity. Besides setting up the very fundamentals of heredity himself, he did the thorough task of cross-breeding pea plants and documented the pattern of inheritance of their different traits. His work, generally overlooked during his lifetime, later founded the base of modern genetics.

Mendel’s Experiments

Gregor Mendel was the Father of Genetics. Born in what is now the Czech Republic, Mendel entered the Augustinian monastery in Brno, where he conducted his famous experiments with pea plants. He was systematic in his approach and statistical in the analysis of trait inheritance, which was far ahead of his contemporaries.

Mendel worked with pea plants that expressed seven distinct traits: flower colour, seed shape, pod colour, pod shape, flower position, seed coat colour, and stem length. By cross-breeding plants with different traits and analysing a large number of progenies, he discovered that trait inheritance occurred in a very regular fashion. His careful breeding experiments and meticulous record-keeping led to the formulation of three basic laws of inheritance.

In this respect, Mendel cross-pollinated plants that had antithetical traits and traces the transmission of these features in consequential generations. He, in this way, established that plant traits do not blend but are passed down in discrete parcels—which he referred to as "factors," now called genes. This research laid clear explanations for dominant and recessive traits, introducing this study into modern genetics. His findings were published in 1866, but the world forgot them until the beginning of the 20th century when they were rediscovered, celebrated, and confirmed by other scientists.

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Mendel's Laws of Inheritance

Through pea plant experimentation, Gregor Mendel founded some of the fundamental principles of genetics that explain heredity in organisms from one generation to another.

Law of Segregation

Mendel's first law is the Law of Segregation, that, during gamete formation (the production of eggs and sperm), the two alleles of a trait separate, or segregate, so each gamete is passed only one allele for each trait. In other words, if there is a plant having an allele for purple flowers (P) and an allele for white flowers (p) while making gametes, these will separate on their own, as some gametes receive P and others p.

Law of Independent Assortment

Mendel's second law, the Law of Independent Assortment, states that the alleles for the different traits segregate independently of each other while forming gametes. This simply means that the inheritance of another trait will not interfere with the working of the inheritance of some other. For instance, the allele segregation concerning seed colour (yellow or green) is independent of that of seed shape (round or wrinkled).

Law of Dominance

According to Mendel's third law, the Law of Dominance, if two alleles for a certain trait exist, then one allele will be expressed over the other allele. In his experiments with the flowers, plants with the genotype Pp had purple flowers since the allele for purple flowers, P, was dominant over that for white flowers, p.

Mendelian Traits and Terminology

In Mendelian genetics, certain terms are defined for the constituent elements and products of inheritance.

Mendelian Crosses

Mendelian crosses are experiments in breeding applied to the study of inheritance involving jointly specific traits.

Monohybrid Cross

A cross dealing with one trait. For example, Crossing a homozygous dominant, PP, plant with one that is homozygous recessive, pp, will result in an offspring all heterozygous, Pp, expressing the dominant phenotype.

Dihybrid Cross

A dihybrid cross involves the crosses of two traits. For instance, plants can be crossed heterozygous for seed colour (Yy) while, at the same time, heterozygous for seed shape (Rr). This will then give an offspring neither, one, nor even both traits. The ratio of phenotypes of offspring is usually in a 9:3:3:1 ratio.

Applications of Mendelian Genetics

Applications of Mendelian genetics can be broadly found in human genetics, plant and animal breeding, and medical genetics. The working geneticist needs an understanding of the principles of heredity to predict the occurrence of genetic disorders, the development of new crop varieties, and the improvement of livestock by selective breeding.

In human genetics, it helps in genetic counselling and diagnosing hereditary diseases owing to its Mendelian pattern of inheritance. Breeders apply Mendelian principles to the genetic improvement of highly desired traits in plants and animals for greater productivity and sustainability in agriculture. Applications in these areas underscore the core role Mendelian genetics plays, both in basic research and in intervention strategies.

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