Question

When crossing a true-breeding red snapdragon flower with a true-breeding white flower of the same species, we secure all pink offspring. This would seem to support the pre- Mendel view that inheritance is a blending of parental traits. However, Mendel and conventional wisdom agree that "blending" of parental traits is not correct and that particles of inheritance are actually involved because:
1) in the case of incomplete dominance, only radioactive isotope tracers can follow the actual hereditary particles.
2) under blending theory, over many generations only the average (or pink flowers) would remain; there would be no way to get back to pure red and white.
3) it is possible to cross the pink F-1 generation and secure a predictable proportion of pure red and white flowers again, which is not accounted for under the blending theory.
4) None of the above is true.

Answer 1

Answer:

2) under blending theory, over many generations only the average (or pink flowers) would remain; there would be no way to get back to pure red and white.

3) it is possible to cross the pink F-1 generation and secure a predictable proportion of pure red and white flowers again, which is not accounted for under the blending theory.

Explanation:

According to blending theory, parental traits mix to produce a blended trait in next generation. Particles of inheritance which are factors or alleles have no role in it. But Mendel proved that traits do not blend and factors carrying them are present in some combinations in next generation.

Here, Pink flowers are produced when red and white flowering plants are mated in snapdragon. This might first appear as an instance of blending but particles of inheritance are still involved. This can be proven if the pink flowers are crossed with pink flowers or other colour flowers. A proportion of offspring flowers will be red and white like original plants. This would not be possible if traits kept blending giving rise to only pink flowers.

For example if two pink flowers are crossed, all three types of flowers i.e. red, white and pink will be obtained in next generation. This is only possible if they are being controlled by some factors and they come together in some combination to give rise to original colour of flowers.