Question

Which of the following conclusions can be drawn from the given figure?

• A. It shows Mendel's monohybrid cross.
• B. The ratio of violet and white flowers is 3 : 1.
• C. Violet flowers are dominant.
• D. All of the above.

Answer 1

Answer: (D)

All of the above.

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 violet colour, and lowercase letters represent the recessive trail, the white colour. The above cross represents two homozygous individuals, one with the dominant trait (violet flowering plant, VV) and the other with the contrasting recessive trait (while flowering plant, vv). The F${}_1$ generation of these resulted in all heterozygous individuals (Vv). The F${}_1$ generation is self crossed to produce the F${}_2$ generation and the results are homozygous and heterozygous violet flowering plants (VV, Vv) and homozygous white flowering plants (vv). Mendel's experiment and his resultant statistical analysis showed that the total offspring of the F${}_2$ generation was 75% violet flowering plants and 25% white flowering plants or a 3:1 ratio. If two homozygous traits are crossed, the phenotype of the F${}_1$ is called the dominant trait. When two F${}_1$ plants are crossed, the F${}_2$ phenotype will have representatives of the dominant trait and the recessive trait (the recessive trait will remain hidden in the F${}_1$ and reappears in the F${}_2$). The phenotypic ratio in the F${}_2$ will be 3:2:1, dominant to recessive. Therefore, the F${}_2$ generation of a monohybrid cross, with dominance will result in phenotypic ratio of 3:1 and genotypic ratio of 1:2:l.