Heredity | Class 10 Science Notes

Inheritance of Traits Over Generations

This section elaborates on how traits are inherited over multiple generations, using Mendel's pea plant experiments as a model. When two pure-breeding plants with contrasting traits (e.g., round seeds and wrinkled seeds) are crossed, the first generation (F1) offspring all exhibit the dominant trait (round seeds). This shows that the dominant trait masks the recessive trait in the F1 generation. However, when F1 plants are self-pollinated, the recessive trait reappears in the second generation (F2) in a predictable ratio of approximately 3:1 (dominant: recessive). This pattern demonstrates that traits are controlled by pairs of alleles, with one allele inherited from each parent. The section also introduces the concept of genotype (genetic makeup) and phenotype (observable trait), explaining that the phenotype depends on the combination of alleles present. The segregation of alleles during gamete formation ensures that offspring receive one allele from each parent, maintaining genetic variation. The section uses Punnett squares to illustrate how alleles combine to produce different genotypes and phenotypes in offspring.

📊 Diagram: Figure 8.3 Inheritance of traits over two generations

🧪 Activity: Performing a monohybrid cross using pea plants to observe trait inheritance over two generations.

🔗 Connection: This section prepares the understanding needed to explore inheritance of two traits simultaneously and the principle of independent assortment.