Classical Genetics
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Classical Genetics
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Did you know that the foundation of everything we know about genetics started in a quiet monastery garden? Yes, It was the Gregor Mendel, often called the "Father of Genetics," was an Austrian monk who, in the mid-1800s, made one of the greatest scientific discoveries using simple pea plants! [Reference]
Mendel didn’t just randomly grow plants but he carefully cross-bred different varieties and focused on traits like flower color, seed shape, and pod texture. But, what made him different was how he applied a systematic, mathematical approach to study how these traits were passed down through generations something no one else had done before. From his experiments, Mendel discovered that traits are inherited as distinct units, which we now call genes.
He came up with two major ideas: the Law of Segregation (each parent passes one of two possible alleles for a trait to their offspring) and the Law of Independent Assortment (traits are passed down independently of one another). Strangely, even though his experiments were groundbreaking, hardly anyone noticed during his lifetime. It wasn’t until decades later, in the early 1900s, that scientists like Hugo de Vries, Carl Correns, and Erich von Tschermak rediscovered Mendel’s work and realized just how far ahead of his time he really was. [Reference]
Why did Mendel choose pea plants? 🌱
When Mendel set out to study inheritance, he needed an organism that would make patterns of heredity clear and reliable. Instead of using complex plants like roses or oak trees, he chose the simple pea plants a decision that became the foundation of genetics.
Peas were ideal because of their different characteristics, given below:
Clear and visible traits: Pea plants showed obvious differences, like tall vs. short or purple vs. white flowers, making it easy to spot patterns.
Controlled breeding: Mendel could easily hand-pollinate them or let them self-pollinate, giving him full control over the experiment.
Quick life cycle: Peas grew fast and produced lots of offspring, so Mendel didn’t have to wait long to see results.
Easy to grow: They thrived in the monastery garden without needing special care.
Multiple traits to track: Peas had several contrasting traits to study at the same time, giving richer and deeper insights.
Large number of seeds: Each cross gave lots of seeds, which made his results more accurate and reliable.
What characteristics did Mendel study in pea plant?
Mendel carefully selected pea plant traits that were simple, distinct, and easy to observe. Each trait had only two clear contrasting forms, for example, tall vs. short plants, so there was no blending, and inheritance patterns could be followed with clarity. This approach allowed him to uncover the fundamental principles of heredity.
In total, Mendel studied seven key traits in pea plants, which formed the basis of his experiments.
Here are the 7 characteristics he focused on:
Flower Color: Purple 🌸 vs. White 🌼
Flower Position: Axial (along the stem) 🌿 vs. Terminal (at the end) 🌸
Stem Length: Tall 🌳 vs. Short (dwarf) 🌱
Seed Shape: Round ⚪ vs. Wrinkled 🌰
Seed Color: Yellow 💛 vs. Green 💚
Pod Shape: Inflated (full) 🫛 vs. Constricted (pinched)
Pod Color: Green 🟩 vs. Yellow 🟨
Mendel Experiment
Gregor Mendel conducted two key experiments to understand the principles of inheritance, which are now known as the monohybrid cross and the dihybrid cross. These experiments laid the foundation for classical genetics.
A monohybrid cross is a genetic cross between two individuals that are both heterozygous for a single trait. It focuses on the inheritance of a single trait, where the parents differ in one trait controlled by two alleles of the same gene.
A dihybrid cross is a genetic cross between two individuals that are both heterozygous for two traits. It examines the inheritance of two different traits simultaneously, where each trait is controlled by two alleles of different genes.