A mutagenesis screen was conducted to identify plants that were unable to sustai

Question

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 olive1. The remaining two had yellow leaves under high intensity lighting and were called yellow1and yellow2. 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.
a) What evidence indicates that the mutants identified in this screen are conditional?

b) What is the advantage of identifying conditional mutants in this screen?

c) Why were all the mutants crossed to wild-type plants?

Explanation / Answer

a) What evidence indicates that the mutants identified in this screen are conditional?

Conditional mutants exhibit a mutant phenotype only under certain environmental conditions. Each mutant does not exhibit a mutant phenotype in shaded conditions, but it does under high intensity light.

b) What is the advantage of identifying conditional mutants in this screen?

Yellow leaves is normally a lethal phenotype - the conditional nature of these mutations allows you identify mutations that would normally be lethal.

c) Why were all the mutants crossed to wild-type plants?

To test whether the mutations are recessive or dominant.

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