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Incomplete Dominance

Prompt

  1. When round squash are crossed with long squash, all offspring are oval. How many genotypes are produced when round squash are crossed with oval squash? 3
  2. An embryo resulting from the mating of two albino rabbits is transplanted into the uterus of a brown rabbit. The color of the offspring can most reasonably be expected to be (Albino is recessive to brown)
  3. In 4 o'clock flowers, red is dominant to white, but the heterozygote is pink. What is the phenotype ratio of crossing red 4 o'clock flowers and pink 40'clock flowers?
  4. In cattle, red is dominant to white, but the heterozygote is roan. If 2 roans are mated, how many of the offspring will be red if they have 12 calves?

    1. If red flowers were crossed with white flowers, what would the frequency of pink flowers be in the F2 generation?

    2. If 60 offspring are obtained in the F1, how many will be white?

Response

  1. When round squash (RR) are crossed with long squash (rr), all offspring are oval (Rr). If round squash (RR) are crossed with oval squash (Rr), the possible genotypes of the offspring are:

    R R
    R RR RR
    r Rr Rr

    Genotypes produced: RR, Rr.

  2. Since albino is recessive to brown, an embryo resulting from the mating of two albino rabbits (aa) will be albino regardless of the brown rabbit's (Aa or AA) uterus it is transplanted into.

    Offspring color: Albino (aa).

  3. In 4 o'clock flowers, crossing red (RR) with pink (Rr) results in:

    R R
    R RR RR
    r Rr Rr

    Phenotype ratio: 2 Red (RR) : 2 Pink (Rr), which simplifies to 1 Red: 1 Pink.

  4. In cattle, if 2 roan (Rr) are mated, the offspring will be:

    R r
    R RR Rr
    r Rr rr

    Phenotype ratio: 1 Red (RR) : 2 Roan (Rr) : 1 White (rr).

    If they have 12 calves: - Number of red offspring: \( \frac{1}{4} \times 12 = 3 \).

    1. Frequency of Pink Flowers in the F2 Generation

      Crossing red (RR) with white (rr) produces all pink (Rr) in the F1 generation. Crossing two F1 (Rr x Rr) results in:

      R r
      R RR Rr
      r Rr rr

      Phenotype ratio: 1 Red (RR) : 2 Pink (Rr) : 1 White (rr).

      Frequency of pink flowers in the F2 generation: \( \frac{2}{4} = \frac{1}{2} = 50\% \).

    2. Number of White Offspring in F1

      If 60 offspring are obtained in the F1 generation: - All F1 offspring will be pink (Rr).

      Number of white offspring: 0.

      Here's a summary table for Problem 5:

      F1 Generation Phenotype Number of Offspring
      Rr x Rr Pink 60

      If we consider F2:

      F2 Generation Phenotype Ratio Number of Offspring
      RR Red 1/4 \( \frac{1}{4} \times 60 = 15 \)
      Rr Pink 1/2 \( \frac{1}{2} \times 60 = 30 \)
      rr White 1/4 \( \frac{1}{4} \times 60 = 15 \)