The researchers started with a monohybrid hair length phenotypic cross. They use two heterozygous parents to cross one gene. As previously stated in this article, this results in a 3:1 phenotypic ratio, generating both long and short-haired offspring. Despite the fact that some kids have long hair, they inherit the recessive gene for short hair. Long-haired children have a considerably larger chance of having long hair than short-haired offspring.
A second cross was performed, this time incorporating the hair colour gene. Because the two genes now give way to numerous phenotypic outputs, this dihybrid cross will produce more than two phenotypic results. The phenotypic ratio now stands at 9:3:3:1, with the options being long, black hair, long brown hair, short black hair, and short brown hair. We can observe that when additional genes are introduced into the breeding process, the phenotypes get more complicated.
Finally, the third gene was introduced, which contributes to hair texture. The trihybrid cross-ratio, like the monohybrid and dihybrid crossings, may be calculated using a Punnett square calculator. There are a total of 8 observable characteristics in this phenotypic ratio. All of these elements are mixed in unique ways to generate distinct children.
The most common phenotype will be a dark, long, straight-haired human child with a combination of all the dominant genes. This is due to the fact that once the alleles are joined, the dominant allele always takes precedence. The following phenotypes will be observed:
• hair that is long, straight, and brown.
• hair which is long, curly, and black.
• hair that is long, curly, and brown hair.
• hair is short, straight, and black.
• Brown hair which is short and straight.
• hair that is short, curly, and black.
• hair that is short, curly, and brown.
The phenotype aabbddd is the least frequent, as predicted, because it is the only one that includes all three recessive genes. Only one of the sixty-four (64) potential crossovers has a chance of happening.
These illustrations depict phenotypic ratios using one, two, and three genes, respectively. In actuality, the phenotype is controlled by the interplay of numerous genes (alleles) at multiple loci, making the inheritance of human hair characteristics far more complicated.