[pyrnet] Heredibility of recessives

[Patric Lundberg <pyrsrgr8@yahoo.com>]

Joe,

(and pardon me Linda for butting in)

> An ever deminsihing number of
> descendants each 
> generation will be at risk of 50%.

With this statement you are assuming equal use of each dog at every
generation, which we know is not the case.  I think one of Linda's
points was that a popular sire can very quickly increase the carrier
incidence in the population even if all his offspring subsequently are
not used more than average.  However, each time a carrier from those
lines happens to become popular and produce a larger number of
offspring, the incidence in the population again jumps.

So, with the assumption that future dogs are used to an equal level
(that means approximately the same number in subsequent are used, and
used to produce about the same number of offspring), *then* any time a
popular stud is a carrier, then number of carriers takes a leap upwards
in the population.

Without doing some population modelling on this, we can't say when this
accumulation would plateau, but my guess is that a simple recessive
should accumulate until it reaches somewhere between 0-50% of the whole
population being carriers.

> I doubt there is a litter
> from show stock in the USA that does not
> have a dwarf carrier behing it somewhere. 

Show stock or not, this is probably true although there might just be
some old CA lines that have a chance of being "clean" for this
particular affliction.

That said, I'd like to bring up a common saying among geneticists, that
every individual carries around 5 severe genetic problems (most of
which we would never have a clue is there, naturally).  So while you
may think you are in the clear for one "invisible" trait, you are
virtually guaranteed to have a few other problems lurking in the
shadows...

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

__________________________________________________
Do You Yahoo!?
Yahoo! Shopping - Thousands of Stores. Millions of Products.
http://shopping.yahoo.com/