Question

When peas with red flowers are crossed with peas with white flowers and then the resulting plants are AGAIN crossed, what will be the ratio of pea plants with red flowers to plants with white flowers in this SECOND generation?

Answer 1

Answer: Provided that Red flowers are dominant over white flowers and that the flowers used in the crossing are pure breeding flowers (homozygous), using RR to represent red flowers and rr to represent white flowers, when peas with red flowers are crossed with peas with white flowers and then the resulting plants are AGAIN crossed, the ratio of pea plants with red flowers to plants with white flowers in this SECOND generation will be 3 : 1.

Explanation: Crossing the parent plant (RR x rr), all the first filial generations will have red flowers but heterozygous (Rr).

When the first generation is crossed with one another (Rr x Rr), the second generation produced will have 3 red flowers and one white flower.

Check the attached image for better illustration.

Answer 2

Answer:

Red flowers: white flowers 3:1

Explanation:

Gregor Mendel crossed an homozygous dominant pea plant that produced red flowers (RR) and a homozygous recessive pea plant that produces white flowers (rr). He got a F1 generation where all the offsprings were red-flowered heterozygous (Rr).

The hybrids in F1 generation were then self-crossed (see attached image). The phenotypic ratio was 3:1 i.e. 3 red-flowered pea plants to 1 white-flowered pea plants.

RR, Rr, Rr and rr