Homework SourseMenders law of segregation was determined by studying crosse
Solution
Ans. Mendel’s law of segregation was determined by studying monohybrid crosses, while his law of independent assortment was determined by doing dihybrid crosses.
Law of Segregation (First Law): During gametogenesis, the two alleles of a gene segregate (separate) so that each gamete gets only one allele of the gene.
Since the law consider one only gene, the cross leading to this law is monohybrid cross (a cross focusing on a single trait or gene). During the cross, it is observed that two phenotypically identical for a single trait (say, flower color) parents (note: parents are genetically heterozygous) gives rise to progeny some of which differed from the parents phenotypically (Ww x Ww = WW, Ww, Ww, ww; parents have red flower, 3 out of 4 progeny have red color, but 1 progeny has white flower). He concluded that a single trait is regulated by a gene and an organism (diploid) has two copies of the gene. During gametogenesis, each copy of the gene (allele) separate from each other and incorporated into separate gametes. It led to the formulation of las of segregation.
Law of Independent Assortment / Inheritance Law (Second Law): The law of independent assortment is an extension of law of segregation. During gametogenesis, the alleles of different genes segregate independently (segregation of alleles of one gene does not affect the segregation of alleles of other genes).
In other words, the considering two traits simultaneously (say, flower color and plant height), the genes regulating two traits do not interfere with the segregation of each other. That is, each of the two different genes follow law of segregation indecently. For dihybrid crosses, the segregation was thus called ‘Law of independent assortment’ meaning that each gene assorts (separate or say, follows law of segregation) independently.
