Talk:Homology (biology)

From Sajun.org

It is correct to say that human hands and feet are homologous structures? - Dominus

I think that this is a tricky one. Leaves and petals are considered homologous. While arm and leg development clearly share some processes, it is hard to say that they are homologous. Are there mutants that have arms (forelimbs) where their legs (hindlimbs) should be or vice versa? Is there any reason to believe that they were ever identical structures? AdamRetchless 02:14, 17 Mar 2004 (UTC)
I don't think they are considered homologous, as they develop from different tissues in the embryo. Yet they are clearly closely related: there's just a single developmental program encoded in the genome that's called "make a limb". This program is reused for the four limbs, with slight modifications. So hands and feet don't share ancestry, they share an instruction set. AxelBoldt 19:13, 14 Aug 2004 (UTC)


Is a sequence family the same as a gene family? AdamRetchless 02:14, 17 Mar 2004 (UTC)

I don't think I've ever heard the term "sequence family". However, gene family doesn't really cover everything, if we use the usual definition of "gene". For example, regulatory sequences could form a family, but wouldn't be genes. It seems not a very important distinction, though, so I'd move to have only 1 article on the topic. (Perhaps later, though, there'll be enough info to warrant one article focussing on (protein-coding) gene families in particular, and another article on sequence analysis techniques relation to, umm, sequence families.)Zashaw 03:40, 17 Mar 2004 (UTC)
You might like to look at Sequence motif. Peak 06:56, 17 Mar 2004 (UTC)

Just curious about the (widely accepted) definition for genetic homology:

>In genetics, homology is used in reference to protein or DNA sequences, >meaning that the given sequences share ancestry.

How can two naturally occurring DNA sequences not share a common ancestry?

The current definition seems to imply that all naturally occurring DNA sequences that evolved from the earliest life form are homologous.

Are there some tacit assumptions about how life evolved being made? Should the definition be added to or am I missing something obvious?

Cheers

Good point. Homology for sequences should probably be defined as a matter of degree, not as a black-white issue. Some pairs of sequences are vastly more homologous than others, because the common ancestor is closer by. AxelBoldt 19:13, 14 Aug 2004 (UTC)



Someone has requested an article on paralog-, orthlog- and homologous genes. Mabye you should set it up so that the searches for those additional terms are sent here (its beyond my wiki expertise), and flesh out the section a little more- a basic digaram could make it a lot more clear--nixie 04:05, 8 Oct 2004 (UTC)


There are plenty of nice diagrams online. I found this through google (it might not be available without a subscription, but I'm sure there are others). Just search for "ortholog paralog diagram". Someone could use the basic ideas in this diagram to make something similar.

http://genomebiology.com/2001/2/8/interactions/1002/figure/F1