What is Mendelian Genetics?
Mendelian genetics, developed by Gregor Mendel in the 19th century, explains how traits are inherited through genes passed from parents to offspring. It relies on principles like segregation—where each parent contributes one allele per gene—and independent assortment, where genes for different traits separate independently. This framework forms the basis of classical genetics, predicting outcomes like dominant and recessive traits in offspring.
Key Principles of Mendelian Inheritance
Mendel's laws include the law of dominance, where dominant alleles mask recessive ones; the law of segregation, ensuring gametes carry one allele each; and the law of independent assortment for unlinked genes. These principles apply to diploid organisms like humans and plants, helping explain why some traits appear in predictable ratios, such as 3:1 in monohybrid crosses.
Practical Example: Using a Punnett Square
Consider a monohybrid cross between two heterozygous parents (Aa x Aa) for flower color in peas, where A is dominant (purple) and a is recessive (white). A Punnett square shows: AA (25%, purple), Aa (50%, purple), and aa (25%, white), yielding a 3:1 phenotypic ratio. This visual tool simplifies predicting genotypes and phenotypes for dihybrid crosses too.
Applications and Importance of Punnett Squares
Punnett squares are vital in agriculture for breeding crops with desired traits, in medicine for assessing genetic disorder risks like cystic fibrosis, and in education for teaching probability in inheritance. They clarify misconceptions, such as assuming equal inheritance chances, and support modern genetics by modeling simple scenarios before complex genomic analysis.