Global Regulators Of Dvelopment Flashcards
What Exactly are HOX genes?
HOX genes are a subset of the
homeobox family of genes:
- Homeobox refers to a DNA binding domain (about 60 amino acids) of the encoded protein (approximately 180 nucleotides)
- This DNA binding domain is called the homeodomain
• In humans there are many homeobox genes, estimations are:
‒ 235 functional genes ‒ 65 pseudogenes
- Many functions
- Many associated disorders
HOX genes do what?
Encode transcription factors
What are the parts of transcription factors?
Activation/repression domain
Dimerozation domain
DNA binding domain
Describe the Collinear development of HOX genes during development
Collinear expression of HOX genes during development
- HOX genes are arranged in clusters
- As a body segment (or body part) needs instruction to develop, the next HOX gene is expressed.
‒ Sequential expression during development controls body part formation during development
• Usually, genes are found scattered in the genome, not arranged in clusters
‒ Consider genes that control pathways such as glycolysis, or purine biosynthesis
‒ These genes might be found on any chromosome, in any location (not clustered together)
Hen were HOX genes discovered?
HOX genes were discovered in the 1980s in the fruit fly.
A striking example is the antennapedia mutation. Here, legs grow from the head of a fly instead of the expected antennae
What disorders are associated with HOX gene mutations?
- An extra cervical rib
- Polydactyly
- Increased risk for cancer
• The most severe phenotypes are not seen
‒Maybe comparable to antennapedia in drosophila
‒Maybe this effect would be too severe to support human life?
What disorders are associated with mutation of the various genes in the large homeodomain family are diverse?
• More than 180 different disorders ‒Eye development ‒ Stature ‒Head development ‒Face development ‒Tooth development ‒ Cancers ‒Wide variety of disorders
