[pyrnet] Gene changes causing dwarfism (was Dwarf/dwarf...)

[Patric Lundberg <pyrsrgr8@yahoo.com>]

Linda,

> Is he the same "kind" of dwarf that we are accustomed to
> seeing?  We just don't know that.  He is actually more similar to
> many Mal dwarfs than are our typical 13", 35 pounders.

What I'm about to go through is not a really addressing the current
discussion but rather a minor excursion into the genetic possibilities
behind gene alterations that result in a given phenotype (in this case
dwarfism).  I thought it might help people with less exposure to
genetics understand some aspects of the discussion better

Linda's statement could be confusing considering it has been mentioned
several times how this phenotype comes from a single autosomal
recessive gene - how could a single gene result in different kinds of
dwarfs?

First off, there could be more than one gene, but I'll meander through
how this could also be the case with a single gene.

Think of genes as words giving an instruction.  In order to get the
correct instruction, the words have to be spelled correctly and follow
each other in the right order:

"Please, could you pick up that axe and hand it to me?"

For the sake of argument, let's say the dwarfism we see in Pyrs come
from the following mis-ordered gene:

"Please, could you axe my hand and pick it up too?"

That is a perfectly reasonable sentence, but the instruction isn't...
The result is that the gene will not give the result needed and we get
a dwarf.  Now, if we make a much lesser change:

"Please, could you pick up that fax and hand it to me?"

This one sound pretty close to the right instruction, but the change of
object will not allow us to chop wood like we had planned, so the
instruction still failed.  We can liken this to the larger than usual
dwarf - while the body does grow larger, it still shows clinical
measures of being a dwarf (such as the Xrays will reveal).

Of course, there are also other ways of getting a flawed instruction,
such as terminating the sentence early (resulting again in a completely
nonsensical instruction), or omission of something crucial:

"Please, could you pick?"

or

"Please, could you axe hand it to me?"

The dwarfism discussion often involve the assumption of a single gene
disruption in an individual dog some time in the past, but that does
not preclude the same or another genetic change to occur independently.

As a real life example, consider the different versions of von
Willebrands in different breeds of dogs - as far as I know, each breed
has to have its own unique test as the genetic changes are different
(and the resulting phentypes also vary).

Anyway, I hope this helped someone follow the thread better (email me
privately if I was unclear on any given point).

Later, Patric



=====
"Sage Advice Improves with Thyme"

Patric Lundberg, PhD
patric@pyrealm.com
Department of Virology
City of Hope National Medical Center
(626)359-8111 x2612

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