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Gregor Mendel was born on July 22, 1822 in Heizendorf (now Hyncice, Czech Republic), into a peasant family. Family and economic difficulties forced him to delay his studies. He was a man of ill-tempered background and humble and withdrawn. The sociocultural environment influenced his scientific personality, mainly the direct contact with the nature, the teachings of his father on the cultivations of fruit trees and the relation with. different professors throughout his life, especially Professor J. Scheider, expert in pomology. On October 9, 1843, he entered the convent of Brunn, known at the time for his great reputation as a center for studies and scientific work. After three years, at the end of his training in theology, he was ordained a priest, on August 6, 1847. At first he was induced by his superior to dedicate himself to the field of pedagogy, but he chose a very different path. In 1851 he entered the University of Vienna, where he studied history, botany, physics, chemistry and mathematics, to graduate and practice as a professor of biology and mathematics. During his stay there he came to give numerous classes as a substitute, in the subjects of mathematics, natural sciences and general sciences, with excellent approval among the students. However, once he finished his studies, he failed to graduate, so he decided to return to Abbot's monastery in 1854. With a calm nature and mathematical mentality, he led an isolated life, devoted to his work. Later he was appointed professor at the Brünn Technical School, where he devoted most of his time to researching the variety, heritage and evolution of plants, especially peas, in a monastery garden for experiments. Their contributions to the world of science are considered today as fundamental for the development of genetics.

Mendel was fortunate to have, in his own monastery, the necessary material for his experiments. He began his studies studying bees, collecting queens of all races, with which he carried out different types of crosses. Between 1856 and 1863 he carried out experiments on the hybridization of plants. He worked with more than 28,000 plants of different variants of the sweet pea or pea, analyzing in detail seven pairs of characteristics of the seed and the plant: the form of the seed, the color of the cotyledons, the shape of the pod, the color of the immature pod, the position of the flowers, the color of the flowers and the length of the stem.

Genotype : Genetic endowment of the individual for a given character or the total set of genes that the individual has. Ex .: AA, Aa, aa.

Phenotype : Observable expression determined by the genotype, ie what is expressed and can be seen. Example: Yellow, green, smooth, rough.

Allele : Each of the gene variants that determine a character. Genes alleles are the ones that convey the same character. Generally one is dominant (A) and another recessive (a).

Dominant Allele : The one that transmits a character that always manifests itself. It is represented by a capital letter. Example: A, L.

Recessive allele : The one that transmits a character that only manifests itself if the dominant allele is not present. It is represented with a lowercase letter, corresponding to the one of the dominant one. Example: a, l.

Homozygous or Pure : Individual with the genotype for a given character composed of two identical alleles. That is, the gametes will be identical for that character. Ex .: AA, aa, LL, VV. When studying two characters, we will say that it is Dihomocygótico that has the two identical alleles for each of the characters. Example: AALL (dominant dihomocygótico), aall (Dihomocigótico recessive).

Parental Generation (P): These are the parents who cross to obtain the next generations ("Parents").

First Generation Branch (F1): Descendants result of the crossing of individuals of the Parental generation ("Children"). Second Generation Branch (F2): Descendants result of the crossing of individuals of the first filial generation ("Grandchildren"). The Law of Uniformity

If you cross two pure lines that differ in one character, the first filial generation is uniform and consists of identical individuals who present only one of the paternal alternative characters.

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Mendel studied the color of the peas and determined that the yellow color was dominant over the green; therefore the A allele that gives the yellow color dominates over the allele to which it gives the green color (A> a). Mendel crossed individuals with AA x aa genotype and yellow and green phenotype respectively. The first law of Mendel is also true for the case where a given gene gives rise to an intermediate and non-dominant inheritance, as is the case of the color of the flowers of the "night dondiego" ". When crossing the plants of the variety of white flower with plants of the variety of red flower, plants of pink flowers are obtained, as can be observed below:

Mendel's Second Law : Law of independent segregation of characters.

which are transmitted from generation to generation are separated (segregan) in the parental and are randomly joined in the descendants to define the characteristics of the new individuals.

Mendel self-fertilized individuals who had appeared to him in the F1 of the previous crossing with an Aa genotype and a Yellow phenotype.

The backcrossing test, or simply cross-testing, serves to differentiate the homo-heterozygous individual. It consists of crossing the dominant phenotype with the homozygous recessive (aa) variety.

- If homozygous, all offspring will be equal, in this case the first Mendel Law is fulfilled. is heterozygous, in the offspring the recessive character will reappear in a proportion of 50%.

Mendel's Third Law : Law of independent distribution or free combination of hereditary characters.

, segregations of genetic factors do not interfere with each other; that is, factors that determine one character are inherited independently of those that determine the other.

Mendel studied the color and shape of the peas to reach their conclusions. As with color, he observed that the smooth form was dominant over the rough, determining that the allele L (smooth) dominates over the rough (L> g). He crossed dominant dihomocygotic individuals (AALL genotype and smooth yellow phenotype) with recessive dihomocygotic individuals (aall genotype and rough green phenotype). The results allow us to appreciate that characters are randomly mixed, from which the third law of Mendel or law of independence of characters is deduced: the different characters are inherited independently of each other and are combined at random in the offspring. p>

Genetics, since the time of Mendel, has advanced a lot. Soon other researchers found exceptions to their laws and showed that they were not always valid. Although it is essential to recognize its importance as a pioneer, geneticists often say that "had a lot of luck" in choosing the species and the characters.

Now let's look at a couple of excellent presentations about Mendel's laws:

  • Adam Floyd