Question

Explain the law of dominance and explain the law of segregation giving examples of both..

Answer 1

Law of Dominance:

1. Law of dominance is known as the first law of inheritance.
   
2. Each character is controlled by distinct units called factors, which occur in pairs.
   
3. If both the factors are present in the organism, one act as dominant over the other.
   

Explanation:

1. Law of dominance explains that in a monohybrid cross between a pair of contrasting traits, only one parental character will be expressed in F₁ generation and both are expressed in F₂ generation in the ratio 3:1.
   
2. The one which expressed in F₁ generation is called dominant trait and the one which is suppressed is called recessive trait.
   
3. In simple words, the law of dominance states that recessive traits are always dominated or masked by dominant trait.​
   
4. For example, when pea plants with round seeds (RR) are crossed with plants with wrinkled seeds (rr), all seeds in F1 generation were found to be round (Rr).
   
5. When these round seeds were self fertilized, both the round and wrinkled seeds appeared in F2 generation in 3: 1 ratio.
   
6. Hence, in F1 generation, the dominant character (round seeds) appeared and the recessive character (wrinkled seeds) got suppressed, which reappeared in F2 generation.

Law of Segregation

1. Law of segregation is the second law of inheritance.
   
2. Law of segregation states that the pair of alleles segregates from each other during meiosis (gamete formation) so that only one factor will be present in each gamete.
   

Explanation:

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