Explain
3. What is the principle of segregation and how is this principle demonstrated in the results of Mendel's monohybrid crosses
The principle of segregation, also known as Mendel's first law, states that during the formation of gametes (reproductive cells), the two alleles (forms of a gene) for a trait separate from each other so that each gamete carries only one allele.
Mendel's monohybrid crosses are experiments in which he crossed pea plants that only differed in one trait, such as flower color (let's say purple and white). He also ensured that the parent plants were homozygous for each allele, meaning that they both carried two identical alleles for the trait (either two purple or two white alleles).
When Mendel crossed a homozygous purple plant (PP) with a homozygous white plant (pp), he observed that all the offspring (known as the F1 generation) had purple flowers. This suggested that the purple allele was dominant over the white allele.
However, when he allowed the F1 generation plants to self-fertilize (cross-pollinate with one another), he found that the next generation (known as the F2 generation) had a ratio of 3:1 for purple to white flowers. This demonstrated the principle of segregation.
According to the principle of segregation, within the F1 generation, the two alleles for flower color (P and p) separated during the formation of gametes. This means that each F1 plant produced gametes carrying either the P allele or the p allele.
In the F2 generation, when the F1 plants self-fertilized, the gametes from each plant could combine in several different ways. The possible combinations include PP (purple), Pp (purple), and pp (white). These combinations resulted in the observed phenotypic ratio of 3:1 for purple to white flowers.
In conclusion, the principle of segregation is demonstrated in Mendel's monohybrid crosses as it explains how different alleles for a trait separate during gamete formation and how they recombine in the offspring, leading to specific phenotypic ratios in subsequent generations.