In radishes, recessive allele causes lack of fur pigmentation (a\" white tiger\"

ID: 89443 • Letter: I

Question

In radishes, recessive allele causes lack of fur pigmentation (a" white tiger") and a second allele causes a cross-eyed condition. If two phenotypically normal tigers that are heterozygous at these loci are mated, what percentage of their offspring are expected to the white? What percentage will be cross - eyed? What percentage will be phenotypically normal for both traits? Incomplete Dominance In radishes, root color shows incomplete dominance. A cross of red and white radishes produces an F1 of all purple radishes. If you crossed two purple radishes, what would be the expected phenotypic ratio? Pea plants usually have white or purple flowers. A strange pea-plant variant is found that has pink flowers. A self-cross of this plant yields the following phenotypes: 30 purple flowers, 62 pink flowers, and 33 white flowers. What mode of inheritance can you infer for flower color in this variant? Explain your answer.

Explanation / Answer

1. In tigers using the Punnett square where P stands for normal pigmentation and p stands for white

25% will be white (pp) and these offspring will also be cross-eyed.

And rest of the 75% offspring will be phenotypically normal for both traits.

2. The color of radish is controlled by two pairs of alleles that sort independently and show no dominance. The R allele produces red radishes and R’ allele produces white. The purple radishes are produced by RR’ heterozygous plant.

RR * R’R’ – monohybrid cross

RR’- F1 generation All the F1 progeny have 100 % RR’ genotype are 100% purple phenotype.

RR’ * RR’ - F1 cross

Using Punnett square;

The expected phenotypic ratio is 3 purple:1 white.

3. The F1 generation plant has pink colour flowers which when self-crossed yielded plants with purple flower, pink flower and white flower in the ratio 1:2:1 (30:62:33).

The blending of colour occurs in the phenotype due to incomplete dominance resulting in intermediate expression of a trait.

The purple and white flowers are homozygous while the pink are heterozygous. The pink flowers result because the purple allele is unable to code for production of enough pigment to make the petals purple in colour.