The gene for the round shape of the fruit in tomatoes dominates over the gene for the pear shape.

The gene for the round shape of the fruit in tomatoes dominates over the gene for the pear shape. From the tomato seedlings planted in the vegetable state farm, 5206 bushes yielded round fruits and 5199 bushes – pear-shaped fruits. What are the genotypes of the parent plants?

Let us denote the gene that determines the development of the pear-shaped fruit by the letter “a”, and the corresponding dominant gene, which is responsible for the development of round fruits, will be “A”.

Then tomatoes with pear-shaped fruits – aa, because homozygosity is a condition under which a recessive trait acquires the ability to be realized in a phenotype. Such a genotype is possible in the offspring of individuals with at least one recessive gene, therefore, the parent individuals are Aa or aa, and their fruits are both round and pear-shaped. Such individuals produce the following sex cells: Aa – A and a; aa – a-type.

Among the offspring of the seedlings planted in the vegetable state farm, the splitting according to the color of the fruits was approximately 1: 1.

If the plants with round tomatoes were AA, then the offspring would split according to the shape of the fruit in a ratio of 3: 1, but, according to the condition of the problem, the proportion is different.

Among the offspring of plants Aa and aa, the following options are possible:

Round fruit tomatoes (Aa) – 50%;

tomatoes with pear-shaped fruits (aa) – 50%.

The proportion is 1: 1.

Answer: Aa and aa.