Question

How can two organisms have the same phenotype but different genotypes?

Answer 1

The term phenotype refers to an organism's observable physical properties which include the development, appearance, and behavior of the organism. A genotype is the complete set of genetic material from an organism. However, genotype is sometimes used to refer to a single gene or set of genes.

Complete answer:
A phenotype is the observable traits of an individual, such as height, color of the eye, and type of blood. The genetic contribution is called the genotype to the phenotype. The genotype largely determines some characteristics, while other characteristics are largely determined by environmental factors. A genotype is the collection of genes from an individual. The term can also refer to a specific gene for the two alleles inherited. The genotype is expressed when protein and RNA molecules are made using the information encoded in the DNA of the genes. Due to the presence of a dominant allele, the same phenotype but distinct genotype is possible. A dominant allele always expresses itself when it is present in the genotype. On both homologous chromosomes, a person can have a dominant allele, while another person may have a single dominant allele and a corresponding recessive allele. In both of the above cases, the dominant allele-controlled trait will be expressed. Therefore, there will be no phenotype distinction. This phenomenon is observed in all organisms, including plants. A dominant allele is a variation of a gene that, even in the presence of other alleles, will produce a certain phenotype. The other allele is known as recessive when a dominant allele is entirely dominant over another allele. Recessive alleles only demonstrate their effect if the individual has two copies of the alleles.

Hence, due to the presence of dominant alleles in the genotype of organisms, phenotypes appear the same even though they differ in the genotypes.

Note:
In both homozygous dominant and heterozygous dominant individuals, dominant eye colour is expressed in humans. There could be different genotypes in two mice that look virtually identical.But if they have visibly different traits, one has white fur and the other has black fur then they have different phenotypes.