question_answer 42)

    In a monohybrid cross of plants with red and white flowered plants. Mendel got only red flowered plants. On self-pollinating these F1 plantsgot both red and white flowered plants in 3:1 ratio. Explain the basis of using RR and rr symbols to represent the genotype of plants of parental generation.  

Answer:

      Generally, upper case letters are used as symbols for dominant and lower case for recessive traits of the same gene (alleles). Experiment shows that it is a monohybrid cross with 3 : 1 ratio in -generation. This shows parents must be true-breeds. As parents are diploid and homologous chromosomes carry alleles with similar type they are represented with RR andrr.