A homozygous tall plant with red flowers (TTRR) is crossed with a homozygous dwarf plant with white flowers (ttrr). Determine the F1 genotype, F2 phenotypic ratio, and explain how Mendel's dihybrid cross principles apply to independent assortment of alleles.

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Problem Analysis and Step-by-Step Solution Step 1: Identify Parental Genotypes and Phenotypes Parent 1 (Tall, Red Flowers): Homozygous dominant = TTRR Parent 2 (Dwarf, White Flowers): Homozygous recessive = ttrr Step 2: Determine Gametes Produced by Parents Parent TTRR produces gametes of type: TR Parent ttrr produces gametes of type: tr Step 3: Determine F1 Generation Genotype and Phenotype Fusion of gametes TR and tr gives the F1 generation. F1 Genotype: TTrr -> Correction based on standard notation: TtRr (Heterozygous Tall with Red flowers). F1 Phenotype: Tall plants with red flowers. Step 4: Selfing of F1 Generation F1 cross: TtRr × TtRr Gametes produced by F1 plants: TR, Tr, tR, tr (each in 25% or 1/4 frequency). Step 5: Punnett Square / F2 Generation Calculation
Using a 16-square Punnett grid for TtRr selfing: TR gamete combines with 4 types Tr gamete combines with 4 types tR gamete combines with 4 types tr gamete combines with 4 types Step 6: F2 Phenotypic Categories and Ratios Tall and Red (TR): 9 plants Tall and White (Trr): 3 plants Dwarf and Red (ttR): 3 plants Dwarf and White (ttrr): 1 plant Final F2 Phenotypic Ratio: 9 : 3 : 3 : 1 Conclusion on Independent Assortment
The segregation of height alleles (T/t) is completely independent of the segregation of flower color alleles (R/r). This results in new recombinant phenotypes (Tall-White and Dwarf-Red) alongside parental phenotypes in the F2 generation, confirming Mendel's Law of Independent Assortment.