4.1: Introduction
- Describe the different laws of genetics developed by Mendel.
- Utilize Punnett square to perform and follow a monohybrid cross.
- Explain how pedigree trees are constructed and how to use them to study genetic diseases.
We all have traits we inherit from our parents, things such as your hair color or your eye color. But what determines which traits we take after our mother versus our father? Some genetic diseases such as cystic fibrosis run in families. How do we know if a newborn baby is at risk of having the disease? And if he/she is at risk, can we calculate the chance of the risk?
About 150 years ago, an Austrian monk named Johann Gregor Mendel (1822-1884) (Figure \(\PageIndex{1}\)) bred peas in his garden. He was interested in studying several characteristics of pea plants: plant height, flower color, seed color, seed shape, etc. He studied them carefully, and bred them for generations, and worked out several rules of inheritance, now referred to as the Laws of Inheritance . Mendel’s work was not highly regarded when he was alive, but was rediscovered in the early 20th century when several scientists independently verified Mendel’s experimental findings. Today, Mendel is considered as the father of modern genetics .
In this chapter we will explore Mendel's experiments with pea plants, which laid the groundwork for modern genetics. It covers key concepts like the Law of Segregation and the Law of Independent Assortment, explaining how traits are inherited through dominant and recessive alleles. Monohybrid and dihybrid crosses are explored using Punnett squares, with examples of genotype and phenotype ratios.
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- Figure 4.1.1 Johann Gregor Mendel (1822–1884) was a lifelong learner, teacher, scientist, and man of faith. As a young adult, he joined the Augustinian Abbey of St. Thomas in Brno in what is now the Czech Republic. Supported by the monastery, he taught physics, botany, and natural science courses at the secondary and university levels. In 1856, he began a decade-long research pursuit involving inheritance patterns in honeybees and plants, ultimately settling on pea plants as his primary model system (a system with convenient characteristics used to study a specific biological phenomenon to be applied to other systems). In 1865, Mendel presented the results of his experiments with nearly 30,000 pea plants to the local Natural History Society. He demonstrated that traits are transmitted from parents to offspring independently of other traits and in dominant and recessive patterns. In 1866, he published his work, Experiments in Plant Hybridization, in the proceedings of the Natural History Society of Brünn.