A Diagram of the Mutagenesis and Crossing Strategy Used by Nüsslein-Volhard

Multiple Choice

A diagram of the mutagenesis and crossing strategy used by Nüsslein-Volhard and Wieschaus to generate and maintain segmentation mutants is shown. Male flies were exposed to EMS (a mutagen) and mated to a non-mutagenized female. How did the researchers ensure that the offspring of Cross B (i.e., the offspring seen in generation C in the diagram) were heterozygotes that carried a mutagenized chromosome? Please select all that apply.

A) CyO homozygotes die
B) Flies homozygous for segmentation mutations usually die
C) Only male flies were mutagenized
D) The female parent in Cross B carries a temperature-sensitive lethal allele