Problem:

A mutagenesis screen was conducted to identify plants that were unable to sustain green leaves under high intensity lighting. In the M2 generation three mutants were identified. One had olive coloured leaves under high intensity lighting and was called olive

1. The remaining two had yellow leaves under high intensity lighting and were called yellow1and yellow

2. In shaded, or low light intensity conditions, they were all indistinguishable from wild type. When crossed to each other, or to wild-type plants, all the F1 progeny had green leaves under both low and high intensity lighting.

Required:

Question 1: What evidence indicates that the mutants identified in this screen are conditional?

Question 2: What is the advantage of identifying conditional mutants in this screen?

Question 3: Why were all the mutants crossed to wild-type plants?

Please explain all the answers.