A test cross was carried out between a brown rabbit and a white rabbit. Five brown offspring and one white offspring were produced. Use a genetic diagram to show how this indicates that the brown rabbit must be heterozygous.
Important Questions on Inheritance
In a species of plant, the alleles for the tall stem is dominant to short. The two alleles for leaf colour, giving green or white in the homozygous condition are codominant, producing variegated leaves in the heterozygote.
A plant with tall stems and green leaves was crossed with a plant with short stems and variegated leaves. The offspring from this cross consisted of plants with tall stems and green leaves and plants with tall stems and variegated leaves with a ratio of 1 :1. Construct a genetic diagram to explain this cross.
In the sweet-pea plants, the gene A/a controls flower colour. The dominant allele gives purple flower and the recessive allele red flower. A second gene, B/b controls the shape of the pollen grains. The dominant allele gives elongated grains and the recessive allele spherical grains. A plant with the genotype AaBb was test crossed by interbreeding it with a plant with red flowers and spherical pollen grains.
Copy and complete the table to show the expected ratio of phenotypes of the offspring of this cross. The gametes from one parent are already in the table.
