Question

Which one of Mendel’s laws describes the inheritance of alleles for a single character? Which law relates to the inheritance of alleles for two characters in a dihybrid cross?

Short answer

The law of segregation demonstrates the inheritance of alleles for a single character.

The law of independent assortment explains the inheritance of alleles for two characters.

Step-by-step solution

Mendel’s laws of inheritance

To study the inheritance pattern of traits, Mendel chose pea plants for his experiments—he selected and studied seven characters of the pea plant. Each character selected had two opposing variants (one dominant and the other recessive).

Thus, the alternative forms of a gene are called alleles.The alleles of a gene are either dominant or recessive.Mendel postulated three laws based on the observations of the results, which are as follows:

• The law of dominance

• The law of segregation

• The law of independent assortment

Law of segregation

The law of segregation states that alleles of each gene present together segregate from one another during the formation of gametes.The alleles segregate in a way that each gamete receives one allele.

During the formation of gametes, each parent’s alleles segregate randomly into gametes. Thus,gametes produced contain half of one allele and the other half with another allele.

In a monohybrid cross, tall (T) and short (T) pea plants were crossed. Two types of gametes are formed; one contains T allele and another with T allele. Thus, the gametes alleles produced either contain a dominant allele or the recessive allele of the gene but not both alleles together.

Thus, the law of segregation demonstrates the inheritance of alleles of a single character.

Law of independent assortment

The law of independent assortment states that the alleles of two different traits are inherited and sorted independently.

In a dihybrid cross, two traits are crossed. The alleles of trait assort independently from the alleles of another trait. For instance, when pea plants with yellow (Y) and green color (g) seed and round (R) and wrinkled shape (r) were crossed.

Half of the gametes produced contain the Y allele, and the other half contain the y allele. Similarly, half of the gametes contain the R allele and the other half the r allele. Moreover, the segregation of the R and r allele is independent of the segregation of Y and y alleles.

Thus, the law of independent assortment demonstrates the inheritance of two alleles.