In tomatoes, the gene that determines the red color of the fruit is dominant over the gene for the yellow

In tomatoes, the gene that determines the red color of the fruit is dominant over the gene for the yellow color. The 3021 tomato bush obtained from hybrid seeds had a yellow color, and 9114 had a red color. Find how many heterozygous plants are in F1 (first generation).

Let’s designate the gene that causes the yellow color of tomatoes by the letter “a”, the corresponding dominant gene responsible for the development of red fruits will be designated as “A”.

Among the progeny of hybrid seeds, the splitting according to the color of the fruit was 3 (red): 1 (yellow).

Plants with yellow fruits – aa, because homozygosity is a condition under which a recessive trait acquires the ability to be realized in a phenotype. This kind of genotype is possible in the offspring of individuals carrying at least one recessive gene, therefore, the parental hybrid plants are Aa, and their fruits are colored red. Such individuals produce sex cells: A and a.

Among the offspring of hybrid parent plants, the following offspring options are possible:

Red tomatoes (AA) – 25%;

red tomatoes (Aa) – 50%;

yellow tomatoes (aa) – 25%.

Answer: In F1 hybrids – 50% of plants are heterozygous.