The laws of Mendel. The basics of genetics

Gregor Mendel is an Austrian botanist who has studied and described the pattern of inheritance of characters. Mendel’s laws are the foundation of genetics, and to this day they play an important role in studying the effects of heredity and the transmission of hereditary traits.

In his experiments, the scientist crossed different types of peas, differing in one alternative feature: a shade of flowers, smooth-wrinkled peas, stem height. In addition, the use of the so-called "clean lines", i.e. offspring resulting from self-pollination of the parent plant. Mendel’s laws, wording and short description will be discussed below.

Studying and scrupulously preparing an experiment with peas for many years: protecting the flowers from external pollination with special bags, the Austrian scientist achieved incredible results at that time. A thorough and lengthy analysis of the data obtained allowed the researcher to derive the laws of heredity, which later became known as the "Laws of Mendel."

Before proceeding with the description of the laws, it is necessary to introduce several concepts necessary for understanding this text:

A dominant gene is a gene, a sign of which is manifested in the body. It is indicated by an uppercase letter: A, B. When crossing, such a sign is considered conditionally stronger, i.e. it will always manifest itself if the second parent plant has conditionally less weak symptoms. As the laws of Mendel prove.

Recessive gene - the gene in the phenotype is not manifested, although it is present in the genotype. It is denoted by the capital letter a, b.

Heterozygous is a hybrid in whose genotype (set of genes) there is both a dominant and a recessive gene of a certain trait. (Aa or Bb)

Homozygous is a hybrid that has exclusively dominant or only recessive genes that are responsible for a certain trait. (AA or bb)

The laws of Mendel, which are briefly formulated, will be considered below.

Mendel’s first law , also known as the law of uniformity of hybrids, can be formulated as follows: the first generation of hybrids obtained by crossing the clean lines of paternal and mother plants does not have phenotypic (i.e., external) differences in the studied trait. In other words, all daughter plants have the same hue of flowers, stem height, smoothness or roughness of peas. Moreover, the manifested trait phenotypically exactly corresponds to the initial trait of one of the parents.

Mendel’s second law or the law of splitting states: offspring from first-generation heterozygous hybrids with self-pollination or related mating have both recessive and dominant characters. Moreover, the splitting occurs according to the following principle: 75% - plants with a dominant trait, the remaining 25% - with recessive. Simply put, if the parent plants had red flowers (dominant trait) and yellow flowers (recessive trait), then 3/4 daughter plants will have red flowers and the rest will have yellow.

Mendel’s third and final law , which is also called the law of independent inheritance of traits, in general terms means the following: when crossing homozygous plants with 2 or more different traits (i.e., for example, a tall plant with red flowers (AABB) and a low plant with yellow flowers (aabb), the traits studied (stem height and flower shade) are inherited independently. In other words, the result of crossing can be tall plants with yellow flowers (Aabb) or low plants with red ones (aaBb).

Mendel’s laws, discovered back in the mid-19th century, received much later recognition. All modern genetics was built on their basis, and selection was followed by it. In addition, the laws of Mendel are confirmation of the great diversity of existing species.