lethal
lethal | recessive
lethal - all die before end of larval stage | recessive
lethal - all die during embryonic stage | recessive
some die during embryonic stage | recessive
some die during larval stage | recessive
Homozygotes die as late embryos.
btl-b
btl-ii
btl-k
btD
btl-a
Fails to complements: btl-k