What will be the phenotypic and genotypic ratio of F1 progeny in monohydrid and dihybrid cross??
Answers
Monohybrid cross involves single pair of contrasting characters and such crosses form the basics of Mendelian genetics. These crosses occur in all major groups of sexually reproducing organisms. In a monohybrid cross between two homozygous individuals with respect to flower colour, the appearance of the colour is the phenotype and the letters representing it are the genotypic alleles. Uppercase letters represent the dominant trait, the red colour, and lowercase letters represent the recessive trail, the white colour.
Trait: Flower colour
Dominant trait: Red colour
Recessive trait: White colour
The above cross represents two homozygous individuals, one with the dominant trait (red flowering plant, RR) and the other with the contrasting recessive trait (while flowering plant, rr). The F1 generation of these resulted in all heterozygous red flowering individuals (Rr). The F1 generation is self crossed to produce the F2 generation and the results are homozygous and heterozygous red flowering plants(RR, Rr) and homozygous white flowering plants (rr). It is important to point out here that Mendel's experiment and his resultant statistical analysis showed that the total offspring of the F2 generation was 75% red flowering plants and 25% white flowering plants or a 3:1 ratio. If two homozygous traits are crossed, the phenotype of the F1 is called the dominant trait. When two F'l plants are crossed, the F2 phenotype will have representatives of the dominant trait and the recessive trait (the recessive trait will remain hidden in the F1 and reappears in the F2). The phenotypic ratio in the F2 will be 3:2:1, dominant to recessive.Therefore, the F2 generation of a rnonohybrid cross, with dominance, will result in Phenotypic ratio of 3:1 Genotypic ratio of 1:2:l
phenotypic ratio- 3:1
genotypic ratio-1:2:1
dihybrid cross
phenotypic ratio - 9:3:3:1
genotypic ratio - (very complex)