Question

Some inbred strains of the weedy plant Arabidopsis thaliana flower early in the growing season, but other strains flower at later times. Four different Arabdiposis plants (1–4) were crossed, and the resulting progeny were tabulated as follows: Mating Progeny 1 × 2 77 late : 81 early 1 × 3 134 late 1 × 4 93 late : 32 early 2 × 3 111 late 2 × 4 65 late : 61 early 3 × 4 126 late a. Explain the genetic basis for the difference in flowering time. How do you know that among this group of plants, the flowering time trait is influenced by the action of a single gene? Which allele is dominant and which recessive? b. Ascribe genotypes to the four plants. c. What kinds of progeny would you expect if you allowed plants 1–4 to self-fertilize, and in what ratios?

Answer 1

Answer:

a. Let us consider that L is responsible for late and l is responsible for early. From the mentioned data, it can be concluded that allele L or late is dominant over early. By crossing plants 1 and 4 we get the expected ratio of 3: 1, which shows that it follows Mendel's law of dominant.  

b. The genotype of all the four plants are:  

1st plant = Ll

2nd plant = ll

3rd plant = LL

4th plant = Ll

c. If the plant 1 is self-fertilized then the expected progeny will be 3 (late): 1 (early).  

In case if the 2nd plant is self-fertilized, the expected progeny will be only early.  

In case if the 3rd plant is self-fertilized, the expected progeny will be only late.  

In case if the 4th plant is self-fertilized, the expected progeny will be 3 (late): 1 (early).