You become an Evolutionary Developmental Biologist and decide to identify the ge

Question

You become an Evolutionary Developmental Biologist and decide to identify the genes that perform the same function as the C. elegans mom genes, but in a related species of nematode, U. gopherus (Ug), which has not had its genome sequenced, so you take a genetic approach. From observations and blastomere recombination experiments, you know that the 4 cell stage U. gopherus embryo looks very similar to that of C. elegans: the Ug-P2 cell signals to the Ug-EMS cell to specify gut cell fates.

A. In genetic terms, describe the type of screen you would do to identify Ug-mom genes and indicate the classes of phenotypes you would search for. (1-2 sentence total!)

B. You identify 8 mom mutants that define 8 different genes and randomly name them Ugmom-1 to Ug-mom-8. Without performing any molecular biology experiments (no cloning, no DNA or RNA sequencing, no protein purification or mass spec experiments, etc.), how could you subdivide these eight genes into 1) those required for the generation of the inductive signal from UgP2 and 2) those required for reception/transduction of the signal in UgEMS? Explain your reasoning and use drawings if helpful. You have wild type and homozygous mutant hermaphrodites available.

Explanation / Answer

A. Make transposon induces randon mutagenesis and look for phenotypes that get arrested at 4-cell stage. Perform PCR using transposon sequences as target and get the amplicon sequences.

B. If you have the sequence of the genes, you can perform a BLAST search to find out which genes are those. Alternatively you can perform a domain analysis to find out which functional domains these genes have (will not apply to 1., as there is no information what kind of signal mom genes synthesize). Receptors usuallt contain a signal sequence to be localized to the membrane and an enymatic domain, containing serine/threonine kinase or tyrosine kinase.

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