What is Mendelian Genetics?
Mendelian genetics, pioneered by Gregor Mendel in the 19th century, explains how traits are passed from parents to offspring through genes. It focuses on dominant and recessive alleles, where dominant traits mask recessive ones. For example, if a plant inherits a dominant allele for tall height (T) and a recessive for short (t), it will be tall (Tt). This forms the basis for predicting inheritance patterns using simple probability.
Understanding Punnett Squares
A Punnett square is a grid tool used to visualize genetic crosses between parents. It lists parental alleles on the axes, creating boxes for all possible offspring combinations. For a monohybrid cross (one trait), it predicts ratios like 3:1 for dominant to recessive phenotypes in heterozygous parents (Tt x Tt), helping demystify how genes segregate independently.
Practical Example: Predicting Flower Color
Consider two pea plants heterozygous for purple flowers (Pp, where P is dominant purple and p is recessive white). Draw a 2x2 Punnett square: rows and columns labeled P and p. The boxes yield PP (purple), Pp (purple), Pp (purple), and pp (white). This shows a 75% chance of purple offspring and 25% white, illustrating Mendel's law of segregation in action.
Applications and Importance
Punnett squares apply to real-world scenarios like breeding animals, agriculture, and human genetic counseling for traits like eye color or disorders such as cystic fibrosis. They clarify misconceptions, like assuming all offspring inherit blended traits (Mendel's disproved this). Understanding these tools aids in biotechnology, medicine, and evolutionary biology by predicting genetic diversity.