Use of double mutants has been invaluable in studying developmental pathways. In C. elegans, sex is determined by the ratio of sets of autosomes to X chromosomes. A diploid male has one X, and diploid hermaphrodites have two X's. The loss- of- function gene her- 1 produces XO worms that are hermaphrodites, but XX worms are unaffected. Mutation of a second gene, tra, causes the XX to develop as male. Given this information, what would be the phenotype of a tra, her- 1 double mutant?
A) lethality B) a hermaphrodite C) an intersex variant D) a male nematode E) a female nematode
In Drosophila, a developmental mutation called ssa (spineless aristapedia) results in flies with mini leg parts on the antennae. What kind of gene does this mutation affect?
A) a gap gene B) a homeotic gene C) a maternal effect gene D) a segment polarity gene E) a pair- rule gene
The abdominal segments of Drosophila have no appendages. Loss of function of bithorax genes results in appendages forming in these abdominal segments. Therefore,_________ .
A) bithorax normally activates a gene that negatively regulates appendages in the abdomen B) bithorax mutations are necessarily recessive C) ultrabithorax usually acts to oppose bithorax genes D) bithorax genes normally activate appendage- forming genes E) expression of bithorax wild- type genes suppresses all appendage formation