The Law of Dominance

The law of dominance is one of the three laws of inheritance discovered by Gregor Mendel. It states that when two different alleles for a trait are present in an individual, only one of them will be expressed in the phenotype. The allele that is expressed is called the dominant allele, while the one that is not expressed is called the recessive allele.

Explanation

Each gene in an organism has two copies, or alleles, one inherited from each parent. These alleles can be either dominant or recessive. If an individual inherits two dominant alleles or one dominant and one recessive allele, the dominant allele will be expressed in the phenotype. If an individual inherits two recessive alleles, the recessive allele will be expressed in the phenotype.

For example, if an individual has one allele for brown eyes (dominant) and one allele for blue eyes (recessive), they will have brown eyes since the brown allele is dominant. However, if an individual has two alleles for blue eyes, they will have blue eyes since blue is the only allele present.

The law of dominance explains why some traits seem to disappear in one generation but reappear in the next. If an individual with a recessive trait mates with an individual with a dominant trait, all of their offspring will have the dominant trait but carry one recessive allele. If two of these offspring mate, there is a 25% chance that their offspring will inherit two recessive alleles and express the recessive trait.

Conclusion

In summary, the law of dominance states that when two different alleles for a trait are present in an individual, the dominant allele will be expressed in the phenotype. This law is important in understanding how traits are inherited and can help predict the probability of certain traits appearing in offspring.

Dominant allele suppresses the effect of recessive allele. This is 1st law of inheritance called 'law of dominance' . Hence only one allele is expressed. Read the Detailed concept in 12TH NCERT.