What is Phenotype?
- The outer appearance of an individual is called its Phenotype.
- Homologous chromosomes contain the same set of genes on the same locus or they contain the alleles for the same character at the same locus. Alleles are the variations of genes which help us gain a particular
- B and b are two alleles of the same When written together, Bb makes up the genetic makeup of the individual. This genetic makeup is called the individual’s Genotype and the expression of trait which is the colour of the eyes in the individual is called the Phenotype.
Genotype and Phenotype
For example, if the individual has black coloured eyes, the set of genes Bb is the genotype, while the black colour of eyes is the phenotype.
Why does a person have black coloured eyes?
- Black eye colour is dominant over brown. The genes which are always expressed in the individual, even in the heterozygous form are dominant and genes which are only expressed in the homozygous form are recessive.
- In three different genotypes BB, Bb, and bb, the sets BB and bb have the same set of chromosomes. BB has a pair of dominant alleles while bb has a pair of recessive alleles. These forms are called Homozygous forms. The set of genes are either dominant or
they are both recessive. The set Bb is the heterozygous form having one dominant gene and one recessive gene.
Dominant and recessive alleles
- So, a person with the dominant alleles will have black coloured eyes as its phenotype. A person with one dominant gene and one recessive gene will also have black coloured eyes as its phenotype because dominant genes express themselves in heterozygous forms. A person is homozygous for the recessive alleles so his phenotype will be brown coloured eyes.
- Thus, alleles help us determine the genotype and the phenotype of