distinction b/t homeotic genes and master genes?

[student12]

Can anyone tell me the distinction between homeotic genes and master genes? Because afterall, they are both responsible for the regulation of other genes during development.

[herb386]

A master gene is any gene that controls a series of other genes. Like SRY etc. A homeotic gene has to contain a homeodomain so I suppose they are a subset of master genes.

[student12]

So homeotic genes are a type of master gene?
I'm confussed...which term to use under what conditions?

[herb386]

When you're talking about a gene which controls a series of other genes involved in some process then you would call it a master gene.

If you are talking about a master gene which contains a homeodomain sequence then you would call it a homeotic gene.

Master genes can control any process, like SRY which controls the sex of the organism in mammals. Homeotic genes generally control the identity of segments or large scale aspects of a body plan. As far as I know master gene is a general term to describe any gene which controls early regulation of gene expression in any process.

[sdekivit]

in the case of the SRY-gene it is a kind of 'masterswitch' --> the genes it turns on or doesn't turn on determines the way of the sexdetermination.

--> homeotic genes are indeed as already said genes with a homeobox encoding for the homeodomain.

These genes yield homeotic transformations in drosophila.

[student12]

wow...so much terms I am not familiar with...
can someone perhaps explain what a homeobox and homeodomain are?

[herb386]

The homeobox is a DNA sequence which codes for a particular DNA binding domain called the homeodomain.

I have also found out that the definition of a homeotic gene is not that it contains a homeobox as I previously thought. It is actually based in the genes function. A homeotic gene is any gene that causes homeotic transformations (turns one body part into another). There are apparently many homeotic genes that do not contain a homeobox.