The mystery of genetics was discovered in the mid-19th century by Gregor Mendel . He conducted an experiment with pea plants by growing these plants and observing the pattern of inheritance at different stages of generation. This resulted in her crossing two homozygous individuals, resulting in heterozygous offspring. This became known as the monohybrid cross, of which we now offer you more details about what it is and some examples.
What is a monohybrid cross and examples
A monohybrid cross studies the pattern of a particular trait that is displayed in the F2 generation. Two homozygous parents are selected for the monohybrid cross and studies are conducted on one trait, ignoring all other traits. The two true breeding parental lines (homozygous) have two contrasting expressions of the particular trait. Therefore, a monohybrid cross can be defined as a cross of two true reproductive parental lines to study the inheritance of a trait at a locus (the fixed position of a chromosome) of a single gene .
Mendel’s peas
If we look at an example of a monohybrid cross we have to analyze the one that discovered the cross itself. The study of the height of a pea plant that Mendel analyzed. For his analysis, Mendel used a homozygous tall plant (TT) and a homozygous dwarf plant (tt) crossed with each other whose pollination resulted in tall plants . All the hybrid plants were tall. He called this a first generation hybrid (F1) and the offspring were named Filial1 or F1 progeny.
He then carried out a second experiment with the seven contrasting pairs and observed that all the F1 progeny showed a pattern in their behavior, that is, they resembled one parent while the other could be completely absent.
He continued his experiment with self-pollination of F1 progeny plants. Surprisingly, he observed that one in four plants was dwarf while the other three were tall .
He also noted that none of the progeny were of intermediate height, ie no mixing was observed. The result was the same for other plant traits as well, and he called them second generation hybrid and the offspring were called Filial2 or F2 progeny.
Mendel observed that traits that were absent in the F1 generation had reappeared in the F2 generation. He called those repressed traits recessive traits. He also concluded that some ‘factors’ are inherited by the offspring from their parents over successive generations.
These “factors” were later called genes. Genes are responsible for the inheritance of traits from one generation to another. Genes consist of a pair of alleles that code for different traits. If a pair of alleles is the same, that is, TT or tt, those alleles are called a homozygous pair, while those that are different or not identical (for example, Tt) are called a heterozygous pair.
We can say then that the monohybrid cross is responsible for the inheritance of a gene. This prompts geneticists to use the monohybrid cross to observe how homozygous offspring express heterozygous genotypes inherited from their parents.
