There is a variety of raspberries with yellow fruits and a stem without thorns.

There is a variety of raspberries with yellow fruits and a stem without thorns. Another raspberry variety has red fruits and a spiny stem. The red color of the fruit and the thorny stem are dominant, while the yellow color and the non-thorny stem are recessive. What percentage of plants with red fruits and a stem without thorns can be obtained in the second generation from crossing these varieties?

Let’s designate the gene that causes the red color of raspberries as A, then the gene that causes the yellow color of the berries will be a.

Let’s designate the gene responsible for the development of spines as B, then the gene responsible for their absence will be b.

A variety of raspberries with yellow berries and a stem without thorns will be recorded as aavv, gametes produced by such a plant – ab.

A raspberry variety with a red fruit and a thorny stem can be written as AABB, AaBb, AaBB and AABb, since all these genotypes lead to the development of these dominant traits.

Suppose we are dealing with a pure raspberry variety, with the AABB genotype. Such a plant produces AB germ cells.

In the first generation, all plants will have red berries and a thorny stem – AaBb. Such hybrids will produce gametes AB, ab, Ab and ab.

In the second generation, the offspring will look like this:

raspberries with a thorny stem and red berries (AaBb) – 25%;

raspberries with yellow berries and a stem without thorns (aabb) – 25%;

raspberries with red berries and a stem without thorns (Aabb) – 25%;

raspberries with yellow berries and a thorny stem (aaBb) – 25%.

Answer: 25%.