Question

What is the difference between a phenotype and a genotype? Does knowledge of an organism's phenotype always allow you to determine the genotype? What type of experiment would you perform to determine the genotype of a phenotypically dominant individual?

Short answer

The difference between a phenotype and a genotype is that the phenotype refers to the observable physical and biochemical characteristics of an organism, while the genotype is the genetic makeup of an organism, consisting of its specific set of genes. Knowledge of an organism's phenotype does not always allow for the determination of its genotype, as phenotypic variation and environmental influences can affect the expression of genetic traits. To determine the genotype of a phenotypically dominant individual, a test cross experiment can be performed by breeding the dominant individual with a homozygous recessive individual and analyzing the offspring's phenotypes.

Step-by-step solution

Define Phenotype and Genotype

Phenotype refers to the observable physical and biochemical characteristics of an organism, determined by the interaction between its genotype (genetic makeup) and its environment. On the other hand, genotype is the genetic makeup of an organism, which consists of the specific set of genes inherited from its parents.

Phenotype and Genotype Relationship

The relationship between phenotype and genotype can be complex, as multiple genes can influence a single phenotype, and a single gene can affect multiple phenotypes. Environmental factors can also influence the expression of genetic traits.

Determine the Genotype from Phenotype

Knowledge of an organism's phenotype does not always allow you to determine its genotype. This is because individuals with different genotypes can show the same phenotype (phenotypic variation), or individuals with the same genotype can display different phenotypes due to environmental influences or interactions between multiple genes.

Experiment to Determine Genotype of a Dominant Individual

To determine the genotype of a phenotypically dominant individual, you would perform a test cross experiment. In a test cross, the dominant individual is bred with a homozygous recessive individual for the trait in question. By analyzing the phenotypes of the offspring, you can determine the genotype of the dominant parent. If the offspring exhibit both dominant and recessive phenotypes in a 1:1 ratio, the dominant parent is heterozygous (having one dominant and one recessive allele). If all offspring exhibit the dominant phenotype, the parent is homozygous dominant (having two dominant alleles).