1.) Homeotic (Hox) Genes

homeobox

- 180-base-pair segment of DNA found in certain homeotic genes that encodes a DNA-binding protein domain (homeodomain) - Homeobox (on homeotic gene)→ homeodomain (on encoded transcription factor protein)

Hox genes (homeotic genes)

- Genes that determine each segment identity of an embryo along the anterior-posterior (head-tail) axis in bilaterian animals during early embryonic development - Encodes transcription factors that regulate development of each segment structures (e.g., legs, antennae, and wings in fruit flies and vertebrae in humans) - Hox genes correspond to regions of the embryo they affect - Subset of homeotic genes - Homeotic genes → transcription factor proteins

homeosis

- Replacement of a body segment structure w/ another segment structure caused by mutations in homeotic genes (Hox genes) - E.g., legs developing in place of antenna in homeotic mutants in Drosophila

homeodomain

A 60-amino-acid sequence section of the encoded transcription factor that binds to specific regulatory regions of the target genes

gene

A length of DNA that codes for a specific protein

transcription factor

Proteins that regulate transcription of DNA to mRNA (messenger RNA) by binding to a specific gene sequence