Question

A wheat plant that is light green in color is found growing in a field. Biochemical analysis reveals that chloroplasts in this plant produce only 50% of the chlorophyll normally found in wheat chloroplasts. Propose a set of crosses to determine whether the light-green phenotype is caused by a mutation in a nuclear gene or in a chloroplast gene.

Answer 1

Set of crosses:

Wild-type male x light-green female

Light-green male x wild-type female

Step-by-step explanation:

Chloroplast genes are inherited maternally and, therefore it would be expected to observe this mode of inheritance:

- Wild-type male x light-green female >> offspring 100% light green

- Light-green male x wild-type female >> offspring 100 % wild-type

Moreover, nuclear genes are inherited from both parents, and, therefore, in the case of complete dominance, it would be expected to observe the following results:

1- When wild type is dominant:

- Wild-type male x light-green female >> offspring 100% wild type

- Light-green male x wild-type female >> offspring 100% wild-type

2- When light-green is dominant:

- Wild-type male x light-green female >> offspring 100% light-green

- Light-green male x wild-type female >> offspring 100% light green