THE IMPORTANCE OF MENDEL'S WORKS (WITH EXAMPLES) - BIOLOGY - 2025

The main importance of Mendel's work is that his experiments have been fundamental to modern genetics. The famous "Mendelian Laws" managed to explain the transmission of genetic inheritance from parents to children.

Thanks to Mendel, today it is possible to predict the characteristics that children will adopt from their parents, namely probabilities of contracting diseases and even mental capacities and natural talents.

While his experiments began humbly by working crosses with simple pea plants, they later laid the groundwork for the emergence of genetics, a field of study dedicated to studying heredity, the process through which parents transmit characters to their children.

Gregor Mendel, Austrian monk and botanist, was born in 1822 to dedicate his life to religion, science and mathematics.

He is considered the father of genetics after publishing his famous essay on plant hybrids in 1866, and he was the first person to explain how human beings are the result of the joint action of paternal and maternal genes.

In addition, he discovered how genes are transmitted between generations and pointed the way for future geneticists and biologists, who continue to practice their experiments even today.

With his work, he revealed the main terms that genetics uses today, such as genes, genotype and phenotype, mainly.

Thanks to his studies, genetics has made it possible to know the origin of various diseases and to analyze chromosomes and genes in more depth under various branches such as: classical, molecular, evolutionary, quantitative genetics and cytogenetics.

The starting point: understanding Mendel's works

Mendel

The objective of the laws developed by Mendel was to study how certain characters or hereditary factors are transmitted from one generation to another. That is why, between the years 1856 to 1865, he decided to carry out a series of experiments.

Their work consisted of crossing varieties of pea plants taking into consideration their specific traits such as: color and location of the plant's flowers, shape and color of the pea pods, shape and color of the seeds and length of the stem of the peas. plants.

Mendel used the pea Pisum Sativum, because it was readily available and in large quantities; Furthermore, the interesting thing about these plants was that when left to their own devices, they crossed and pollinated each other.

The method used consisted of transferring pollen from the stamen of a plant to the pistil of another type of plant.

Mendel combined a red-flowered pea plant with a white-flowered pea plant in order to see what resulted from the crossing. To later start experiments with that generation resulting from the mixture.

As an example, Mendel took different plants and built different versions of the well-known family trees to study what happened to these characters when they were crossed.

Results and importance of their work

1- Discovery of Mendelian Laws

Mendel's First Law

Called "Law of dominant characters or the uniformity of hybrids." Using this law, Mendel discovered that if a line of smooth-seeded peas was crossed with another line of rough-seeded peas, the individuals that were born from that first generation were uniform and resembled the smooth seed.

When obtaining this result, he understood that when a pure species is crossed with another, the offspring of that first filial generation will be the same in their genotype and phenotypically more similar to the carrier of the dominant allele or gene, in this case the smooth seed.

A more common example: if the mother has black eyes and the father blue eyes, 100% of their children will come out with black eyes similar to the mother, because they are the dominant character.

This law states that "when two purebred individuals are crossed, the resulting hybrids are all the same." As shown in the image, understanding the color yellow as the dominant gene.

Mendel's Second Law

Called "Law of segregation". Mendel discovered that by planting the hybrids from the first generation and fertilizing each other, a second generation was obtained that turned out to be mostly smooth and a quarter rough.

Hence, Mendel wondered how it could be possible that second-generation characters had traits, such as rough, that their smooth-seeded parents did not possess?

The answer is found in the statement of the second law: "Certain individuals are capable of transmitting a character even though it is not manifested in them."

A common example following the Mendelian experiment: a black-eyed mother crosses paths with a blue-eyed father, resulting in children who will have 100% black eyes.

If these children (siblings among them) crossed, the result would be that the majority would have black eyes and a quarter blue.

This explains how in families, grandchildren have characteristics of their grandparents and not only of their parents. In the case represented in the image, the same thing happens.

Mendel's Third Law

Also known as "Law of the independence of characters." It postulates that genes for different traits are inherited independently.

Hence, during the formation of gametes, the segregation and distribution of hereditary traits originate independently of each other.

Therefore, if two varieties have two or more different characters between them, each of them will be transmitted independently of the others. As can be seen in the image.

2- Definition of key aspects of genetics

Hereditary factors

Mendel was the first to discover the existence of what we know today as "genes." Defining them as the biological unit responsible for the transmission of genetic traits.

They are the genes, the hereditary units that control the characters present in living beings.

Alleles

Punnett square, the uppercase yellow letter "Y" represents the dominant alleles (Source: Pbroks13 via Wikimedia Commons)

Considered as each of the different alternative forms that the same gene can present.

The alleles are made up of a dominant and a recessive gene. And, the first will manifest itself to a greater extent than the second.

Homozygous vs heterozygous

Mendel found that all organisms have two copies of each gene, and if these copies are purebred, that is, identical, the organism is homozygous.

Whereas, if the copies are different, the organism is heterozygous.

Genotype and phenotype

With his discoveries, Mendel revealed that the inheritance present in every individual will be marked by two factors:

1. The genotype, understood as the complete set of genes that an individual inherits.

2. And, the phenotype, namely all the external manifestations of the genotype such as: morphology, physiology and behavior of the individual.

3- It opened the way for the discovery of numerous genetic diseases

Mendel's experiments made it possible to discover the so-called “Mendelian diseases or defects”, those diseases that are produced by the mutation of a single gene.

These mutations are capable of altering the function of the protein encoded by the gene, hence the protein is not produced, does not function properly or is expressed inappropriately.

These genetic variants produce a large number of defects or rare diseases such as sickle cell anemia, cystic fibrosis and hemophilia, among the most common.

Thanks to his initial discoveries, today different inherited diseases and chromosomal abnormalities have been discovered.

References

1. Arjona, S; Garrido, L; Couple, G; and Aceituno, T. (2011). Diseases with Mendelian inheritance. Retrieved on August 25, 2017 from pasajealaciencia.es.
2. Arzabal, M. Gregor Mendel and the formation of modern genetics. Retrieved on August 25, 2017 from vix.com.
3. Carnevale, A. The new approach to Mendelian diseases. Retrieved on August 25, 2017 from revista.unam.mx.
4. How can we study heredity? Retrieved on August 24, 2017 from khanacademy.org.
5. Garrigues, F. (2017). Mendel's Laws: Three Commandments of Genetics. Retrieved on August 24, 2017.
6. Gregor Mendel. Retrieved on August 24, 2017 from biografiasyvidas.com.
7. Gregor Mendel. Retrieved on August 24, 2017 from britannica.com.