When a cross between parents with contrasting traits generates offspring with an intermediate phenotype, the dominance relation between the alleles is called incomplete or partial dominance.
For example, if a four-o’clock (Mirabilis jalapa) or a snapdragon plant with red flowers is crossed with a white-flowered plant, the offspring have pink flowers. In this type of allelic interaction neither the red nor white flower color is dominant.
Because neither allele is dominant, The F2 phenotypic and genotypic ratios are identical. because neither allele is recessive, the upper- and lowercase letters are not used as symbols. Instead, the alleles responsible for red and white color are represented as R1 and R2.
Cross
When a cross between true-breeding red-flowered (R1R1) and true-breeding white-flowered plants (R2R2) is performed, all the F1 plants have Pink flowers (R1R2). When the F1 plants are self-pollinated the F2 plants have red, pink, and white flowers in the ratio 1 (R1R1) Red: 2 (R1R2) Pink: 1 (R2R2) White.
Follow Learning Biology on:
No comments:
Post a Comment