MP Board · Class 10 · Science · HeredityExplain Mendel's Law of Segregation with the help of a monohybrid cross.

Mendel's Law of Segregation, also known as the first law of inheritance, states that during the formation of gametes, the two alleles of a gene separate or segregate from each other so that each gamete receives only one allele for each trait. To understand this, let us consider a monohybrid cross between a pure tall pea plant (TT) and a pure dwarf pea plant (tt). During gamete formation, the tall plant produces gametes containing the 'T' allele, and the dwarf plant produces gametes containing the 't' allele. When these gametes fuse during fertilization, the F1 generation is formed with the genotype 'Tt'. Because 'T' is dominant over 't', all plants in the F1 generation are tall. When plants of the F1 generation are self-pollinated, the 'T' and 't' alleles segregate independently during gamete formation. In the F2 generation, through random fertilization, we obtain a phenotypic ratio of 3 tall plants to 1 dwarf plant (3:1) and a genotypic ratio of 1 TT : 2 Tt : 1 tt. This clearly proves that the alleles remain distinct and segregate purely during gamete production without blending.