In a cross between Bb imes Bb, what is the probability of producing a bb offspring?

25% (1/4) The genotypes would be BB (25%), Bb (50%), and bb (25%).

Mendelian Genetics

Q: Which law describes why a Pp flower appears purple rather than a mix of purple and white?

Law of Dominance. The purple allele (P) is dominant over the white allele (p) and masks its expression in the phenotype.

Explore Gregor Mendel's fundamental laws of inheritance through interactive Punnett squares and genetic crosses. Visualize the law of segregation (alleles separate during gamete formation) and the law of independent assortment (genes for different traits segregate independently). Practice predicting offspring genotypes and phenotypes for monohybrid and dihybrid crosses, and understand dominant, recessive, and codominant inheritance patterns.

MENDELIAN GENETICS: THE LAWS OF INHERITANCE

Gregor Mendel established the fundamental principles of heredity through his work with pea plants. His findings formed the basis of **classical genetics**, describing how traits are passed from parents to offspring through discrete units (genes).

MENDEL'S THREE LAWS

1. **Law of Dominance**: In a heterozygote, one allele (dominant) will conceal the presence of another (recessive) for the same trait. 2. **Law of Segregation**: Each individual has two alleles for each gene, which separate during gamete formation (meiosis) so that each gamete carries only one allele. 3. **Law of Independent Assortment**: Genes for different traits segregate independently of one another during gamete formation (assuming they are on different chromosomes).

HOW TO USE THIS VISUALIZATION

1. **Cross the Parents**: Drag a homozygous dominant and a homozygous recessive plant to the breeding area. 2. **Build the Punnett Square**: Watch the F1 and F2 generations appear. 3. **Analyze the Ratios**: Compare the observed phenotypic and genotypic ratios to the theoretical predictions. **Try This**: Perform a monohybrid cross of two heterozygotes (). What percentage of offspring are recessive ()? Is it close to the expected 25%?

AP EXAM CONNECTION

Unit: Unit 5: Heredity (Topic 5.3)
Learning Objective: EVO-2.A

COMMON MISCONCEPTIONS

Thinking dominant traits are always the most common (they are not; e.g., polydactyly is dominant but rare).
Confusing phenotype (appearance) with genotype (alleles).
Believing Punnett squares guarantee exact numbers (they only show probabilities).