Question

What are some examples of recessive genotypes and phenotypes?

Answer 1

Hint: The genotype of an organism is the set of genes in its DNA responsible for a particular trait whereas a phenotype is the physical expression of those genes. In other words, a genotype refers to the genetic characteristics while a phenotype refers to the physical characteristics. The word recessive refers to a trait that is expressed only when the allele is homozygous; a trait that is masked by other inherited traits, yet persists in a population among heterozygous alleles.

Complete step by step answer:
To express a recessive trait, an individual must have two copies of the recessive allele. Recessive alleles are denoted by lowercase letters. An individual with an aa genotype will express a recessive trait; therefore, an offspring must receive one recessive allele from each parent to exhibit a recessive trait. One example of a recessive inherited trait is a smooth chin, in contrast to a dominant cleft chin. The absence of cleft chin is called a recessive genotype. Other examples include dimples, freckles, widow’s peak etc. Attached earlobes, inability to roll one’s tongue, and round (versus almond-shaped) eyes are other few examples of recessive genotypes.
The genotype pairs determine the physical appearance or phenotype for each trait. When both genes obtained from each parent code for the same version of a trait the phenotype will match the genotype. For example, if both genes code for blue eyes, the offspring will have blue eyes. However, if both genes carry different variations of the trait, the phenotype is determined by the dominant gene. For example, the brown eyes gene is dominant while the blue eyes gene is recessive. Unless other factors influence the outcome, the genotype combination of a brown-eye gene from one parent and a blue-eye gene from the other parent will result in a brown-eyed child. Recessive phenotypes are said to be the versions of certain masked phenotypes. One can inherit the alleles for them, but they are not expressed unless only that allele is present. Some examples of this would be the diseases Sickle-cell anemia and Cystic Fibrosis. They are genetic disorders, but you are only affected if you have two recessive alleles for the trait. So technically one could have it, but not know it because of the dominant allele masking it.

Note:
The recessive genotype or phenotype is prominent only when there are two alleles present whereas the dominant genotype or phenotype will be prominent even when there is only one corresponding allele present. An allele is said to be one of a pair of genes that appear at a particular location on a particular chromosome and control the same characteristic, such as blood type or color blindness.

Figure 1: Relation between genotype and phenotype