What is Johann Gregor Mendel’s Law of Dominance?

What is Johann Gregor Mendel’s Law of Dominance?

June 27, 2021 Off By Felso

Law of Dominance

Mendel’s next job was to see what would happen when he pollinated two plants with different characteristics. Accordingly, he chose one tall and one short parent plant. He took pollen from the long one and sprinkled it on the stigma of the short one. When the seeds matured on the short plant, he sowed the seeds to discover the result of the cross. Would the new plant look like the short parent or the long parent? Or would it be of medium length, influenced by the character of both parents? He saw that the breeding seedlings were all tall, like the plants he had pollinated to make the cross.

Mendel’s second step was to find out which plant caused the difference. Is it the plant that he uses pollen or that he uses seeds in production?

Accordingly, he reversed the pollination process, using short plants for pollen and tall plants for seed production. The results were the same as before, and all the offspring were taller.

Mendel then experimented with crossing other characters. He crossed plants with yellow seeds and plants with green seeds. He saw that in the first progeny (F1 generation) of the cross, all of them reproduced with yellow seeds. He produced round-seeded species by crossing wrinkled-seeded species with such round-seeded species. Mendel repeated the crossover experiments until he analyzed seven different characters, with surprising results. He carefully followed the progeny of the cross and named the parent plants he used in the first cross “P”. He named the cross result (product) of said progeny as F1. F1 represented the firstborn. By crossing the F1 progeny of two long peas, he produced the F2 progeny (descendants). It followed the previous path in production. He chose two F1 plants, both tall. He cross pollinated them and planted the seeds to produce the F2 offspring. The results of this crossover were quite remarkable. Some of the plants were tall, while others were short. No plants of intermediate height (medium size) had emerged. 3/4 of the plants produced were tall and 1/4 were short. The reappearance of short plants in the F2 generation was of great significance to Mendel. Thus, F1 plants had the character of unseen brevity. The same results were obtained with crosses of the F1 generation with other characters. Crossing the yellow-seeded and green-seeded parent plants (P) produced 3/4 yellow and 1/4 green peas in the F2 generation. From these results, Mendel established the “Law of Dominance”.

The Dominance Law, known as Mendel’s second law, can be clearly defined as follows: “When two similar hybrids with the same genetic structure are crossed, in the offspring that occurs, the characters from the parents emerge at certain rates (dominant character 75%, recessive 25%). interest.”

Mendel’s first law of inheritance: Long peas crossed with short peas, resulting in the long F1 generation, and the short peas reappeared in the F2 progeny. Mendel suggested that characters are controlled by unknown factors. Today these factors are called “genes”. On this basis, Mendel established the first law of heredity, the Law of Isotype = Isotype.

The Law of Identity (isotype)

This law states that various hereditary characters are controlled by factors (genes) and these factors exist in pairs. Although the genes and chromosomes were not known in Mendel’s time, his “Law of Uniformity” constitutes the basic rules of genetics today. The Law of Isotype (Isotype) can be clearly defined as follows: “When two pure (homozygous) individuals differing in one character are crossed, the resulting F1 offspring are all hybrids and similar to each other.” 100% tall hybrids are formed by crossing long pure peas with short pure peas.

Mendel revealed that tall F1 progeny plants are not like pure tall parent plants. Although these peas were not visible, they carried the factor of brevity. This factor would reappear in the next generation. This reasoning led him to discover the second law of heredity, the Law of Dominance. According to this law, one of the factors (genes) in pairs can mask the other or prevent its presence.

Dominance Law

As with garden peas, length is controlled by a pair of genes. The length gene is dominant over the short gene. Shortness gene is called recessive. In Mendel’s crosses, one parent was pure tall and had both length genes. The other was pure short and had both shortness genes. The individuals of the F1 progeny, the product of their cross, were all tall but hybrids. Although they carried one length and one shortness gene, they emerged as tall because the length gene dominated the shortness gene. Mendel was able to present the results of his study in tabular form. Today, each character is expressed by at least two genes. genetics