homeotic genes

maternal effects genes

-genes whose mRNAs are placed in the egg cell by the mother fly before fertilization -some of the mRNAs are tied to the head or tail end of the embryo and are responsible for setting up the head tail polarity -the maternal effects genes encode regulators of transcription or translation that control each other as well as other genes

gap genes

-if gap genes are missing due to a mutation, there is a large gap in the fly larva- its missing a large chunk of its normal segments -activated through interactions between the protein products of the maternal effects genes -also regulate each other -responsible for defining large multi segment regions of the fly

homeotic genes

-master regulator genes that direct the development of particular body segments or structures -overactivated or inactivated by mutations, body structures may develop in the wrong place, sometimes dramatically so

homeodomain

-most animal homeotic genes encode transcription factor proteins that contain this region -and are called hox genes

hox genes

-turned on by a cascade of regulatory genes; proteins encoded by early genes regulate the expression of later -found in many animals -mutations in human hox genes can cause genetic disorders

pair rule genes

-turned on by interactions between gap genes -their expression patterns are redefined by interactions with one another -appear in multiple stripes along the embryo similar to the segments of the mature fly but slightly offset -when its missing due to mutation there is a loss of structures in the segment regions where the gene is normally expressed