Law of Segregation – Class 12 | Chapter – 5 | Biology Short Notes Series PDF

Law of Segregation: The Law of Segregation states that when any individual produces gametes, the copies of a gene separate so that each gamete receives only one copy. Either of the alleles will be received by the gamete. Observing that true-breeding pea plants with contrasting traits gave rise to F1 generations that all expressed the dominant trait and F2 generations that expressed the dominant and recessive traits in a 3:1 ratio, Mendel proposed the law of segregation.

The law of segregation states that each individual that is a diploid has a pair of alleles (copy) for a particular trait. Each parent passes an allele at random to their offspring resulting in a diploid organism. The allele that contains the dominant trait determines the phenotype of the offspring. In essence, the law states that copies of genes separate or segregate so that each gamete receives only one allele.

Law of Segregation

  • In a monohybrid cross, both the alleles are expressed in the F2 generation without any blending.
  • Thus, the law of segregation is based on the fact that each gamete contains only one allele.​ ​​​​​​
  • The gene for seed color in pea plants exists in two forms.
  • There is one form or allele for yellow seed color (Y) and another for green seed color (y).
  • In this example, the allele for yellow seed color is dominant and the allele for green seed color is recessive.
  • When the alleles of a pair are different (heterozygous), the dominant allele trait is expressed and the recessive allele trait is masked.
  • Seeds with the genotype of (YY) or (Yy) are yellow, while seeds that are (yy) are green.

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