Question

Figure 12.5In pea plants, round peas ( R ) are dominant to wrinkled peas ( r ). You do a test cross between a pea plant with wrinkled peas (genotype rr ) and a plant of unknown genotype that has round peas. You end up with three plants, all of which have round peas. From this data, can you tell if the round pea parent plant is homozygous dominant or heterozygous? If the round pea parent plant is heterozygous, what is the probability that a random sample of 3 progeny peas will all be round?

Short answer

There is a 1/8th probability of random sample of 3 progeny of peas to be round.

Step-by-step solution

Step 1. Given Introduction

According to the question In pea plants, wrinkled peas (r) are recessive to round peas (R). A test cross is done between a wrinkled pea plant with genotype (rr) and an unknown genotype plant that has round peas. This gives three plants with round peas.

A test cross is used to check whether the genotype of the dominant plant is homozygous or heterozygous.

Step 2. Explanation

As the data set is too small it is not possible to be sure the plant is homozygous or heterozygous, by random chance, it might possible plant acquired all dominant traits only even if the recessive gene is presented. If the round pea plant is heterozygous then there is a 1/8th probability that a random pea sample of three progeny will have round peas.