Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Gregor Mendel, the 'Father of Genetics', used the Garden Pea ( ) for his experiments due to its clear contrasting traits and short life cycle.
A Monohybrid Cross is a cross between two plants involving one pair of contrasting characters (e.g., Tall vs Dwarf ).
Law of Dominance: In a heterozygous pair (e.g., ), the trait that expresses itself is called the 'Dominant' trait, while the one that remains hidden is the 'Recessive' trait.
Law of Segregation: During the formation of gametes, the two alleles of a character separate (segregate) so that each gamete carries only one allele for each gene.
Law of Independent Assortment: In a Dihybrid Cross (involving two pairs of traits like seed shape and color), the inheritance of one pair of characters is independent of the inheritance of the other pair.
The Phenotype refers to the observable physical characteristics (e.g., Tall), while the Genotype refers to the genetic makeup (e.g., or ).
Homozygous conditions occur when both alleles are identical (e.g., or ), while Heterozygous conditions occur when alleles are different (e.g., ).
📐Formulae
💡Examples
Problem 1:
A pure tall pea plant () is crossed with a pure dwarf pea plant (). Find the phenotypic and genotypic ratio of the generation.
Solution:
- Parents: . 2. Generation: All (Heterozygous Tall). 3. Selfing : . 4. Genotypes: . 5. Phenotypic ratio is (Tall : Dwarf). 6. Genotypic ratio is ().
Explanation:
According to the Law of Segregation, the alleles and separate during gamete formation. The Punnett square for shows one homozygous tall (), two heterozygous tall (), and one homozygous dwarf ().
Problem 2:
In a dihybrid cross between Round Yellow () and Wrinkled Green () seeds, what is the frequency of Round Green seeds in the generation?
Solution:
Total offspring in . According to the ratio : Round Yellow = , Round Green = , Wrinkled Yellow = , Wrinkled Green = . Frequency of Round Green = .
Explanation:
Due to the Law of Independent Assortment, the traits for seed shape and seed color distribute independently. The Round Green phenotype results from combinations like or .