I just really don't get it.
Have I got this right?
They are genes which control body plan. In these genes is a segment called a homeobox, which is 180 bases long and codes for a protein which is 60 amino acids long. These proteins bind to DNA and switch on or off the process of transcription, which will determine the growth and development of that cell (so either apoptosis or specialisation). All animals have similiar homeobox genes, and so do plants, which is why our body plans are similiar.
Very confused - that doesn't quite match up with my notes or the textbook, but its the only way it makes sense to me :/ Can anyone help?
I think its how genes are aligned on a strand of DNA that codes for the positioning of different parts of the body. The numbers above are about right I duno the exact values
We always get an insect (cannot remember the name) as an example. If there is a mutation in one particular homeobox gene, then they often have a leg instead of an antennae
This is my understanding..........
Homeobox genes: control the development of the body plan
Consist of 180base pairs (the homeobox) which code for polypeps of 60amino acids
SOME are transcription factors, which bind to DNA upstream and initiate transcription, thus regulating expression of other genes
They're arranged in Hox clusters, the more complicated the organism, the more clusters
They're activated and expressed from anterior to posterior
thats the one sorry if I wasn't much help
Yea I just edited it which is kind of important to see, look at the bits in bold because I read just now that homeotic genes are the collective name for genes such as the homeobox gene.
Hox genes are a highly conserved set of genes that are expressed in an anterior-posterior fashion, and responsible for much of the anterior-posterior patterning. Typically, the more posterior you go the more hox genes are expressed (this is true for segmental structures such as rhombomeres (hindbrain precursor), somites (spine precursor), and branchial arches.
Hox genes themselves are important transcriptional regulators that control vast/complex transcriptional cascades that fate restrict cells/cell lineages (with a certain amount of plasticity etc.). They do this by binding to DNA and either directly or indirectly (by recruiting other factors) affecting the speed/efficacy/efficiency of DNA transcription. They can repress OR activate to many different degrees.
They are present in clusters, first described in drosophila (fruit fly) which has a single cluster. Interestingly the clusters are expressed in an anterior-posterior pattern that is closely correlated to how they are arranged along the DNA. Mouse have 2 or 3... (can't remember sorry) and humans have 4 clusters - hoxa hoxb hoxc and hoxd.
They are important in all sorts of things, spinal cord patterning, dermatome, limb patterning, heart, brain, blah blah, you name it it's probably affected by hox genes!
That's a very simple overview, if you want more on anything specific feel free to ask!!!
The binding of hox transcription factors does not by any means have to be at the beginning of a gene, it can be within genes (in introns) or at the end, or even 1000s of bases away at either end. (just trying to clear up something someone else said above..)
Drosophila (fruit fly) i think