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3.2.2. Mendel's second law

Mendel's second law or Law of independent segregation of characters

When two heterozygous individuals of the first generation (F1) are crossed with each other, recessive traits that did not appear in Freappear in Fin a ratio of 3:1.

After the first law experiment, Mendel crossed two individuals of each F1 with each other (or self-fertilized the F1 hybrids), obtaining a second filial generation or F2 with the following results:
1 Smooth x smooth seed 2 5474 Smooth seed and 1850 rough seed (approx. 3:1)
Yellow x yellow seed 6022 Yellow seed and 2001 green (3:1)
Swollen x swollen pod 1882 Sheath swollen and 299 not swollen (3:1)
Colored flowers lilac x lila 705 purple flowers and 224 white (3:1)

With these data, Mendel deduced that each trait or character was determined by two factors, each transmitted by one of the parents who, previously, randomly separated their two pieces of information. He thus proposed the 2nd law called the segregation or disjunction of antagonistic factors or characters and their random combination between descendants.


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Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.