[2-part post combined.]
 
Annette, those usual lifespans (death usually in 7th or 8th year) are the
same as here in the U.S.  at least in our household, with some older and
some younger.
 
Re darkness: the current hypothesis is at least 14 hours of complete
darkness in each 24 an tat is the figure I've usually given (though in
one old writing I have seen 16 hours in each 24 mentioned).  I never
said 18 hours in each 24 unless I hit is a typo at some point and didn't
catch it.
 
Linda wrote:
>It is also important to point out that these types of genetic syndromes
>have variable expression, which means the amount of white, the extent
>of deafness and related issues can vary greatly from animal to animal.
 
>A deaf blaze can have hearing offspring, and a hearing panda can have
>deaf kits.  The only responsible course of action is to STOP BREEDING
>AND PROMOTING these patterns.
 
EXACTLY!  And far better expressed than I could manage.
 
Plus, the concern goes well beyond deafness.  There are some
malformations and other health problems which can be encountered with
neural crest variants, and the KIT oncogene (which looks to more likely
to be the culprit in ferrets a number of the times -- esp. when there is
white spotting beyond just a head blaze -- rather than Waardenburg is an
oncogene, and oncogenes increase vulnerability to malignancies.
 
Darrin writes:
>However, my point being, that after thousands of years of careful
>selective breeding, wherein any undesirable traits where carefully
>"bred out".  we now find ourselves faced with breeders who do not seem
>to care about any of the desirable traits, accept for colors.. i.e.:
>no concern of deafness, or, docility, or health issues..  as long as
>the ferret is "cute" and they can sell them.
 
I STRONGLY AGREE!
 
Darrin also points out that new mutations do happen.  He's right.  If I
recall right the figure suspected a couple of decades ago was 1 in 10,000
alelles bearing a spontaneous mutation without unusual exposure to
substances which induce mutations like radiation, virii, etc.  (I recall
that the figure used then pretty well worked out that every human on
average is going to have a mutation of some sort but most of the ones
which survive are in the noise, also that it was thought that the number
of miscarriages which happen so early that no one even realizes there
was a pregnancy is extremely high and that part of the cause for that
may be mutations which were not viable.  Oh, and don't think that we are
by any means the type of life form with the most alleles.  Many have
more, which kind of surprised some reporters when work on rice came out.)
 
 
Darrin writes:
>many genetic defects have been "introduced" simply because of
>"inbreeding.."
...
>Indeed, inbreeding is one of the major influences on defects..
 
Okay, technically, Darrin what you are talking about is not a genetic
introduction.  It is true, though, that a physical appearance which is
so rare that it is virtually unseen before selective breeding for that
feature can become much more common with inbreeding.  What you are
talking about here is doubling up specific recessive alleles which are
usually hidden under dominant ones.  The results in certain appearances
showing up which would normally be very rare.
 
Recessive and Dominant have *nothing* to do with rates in a population.
Becoming common does not make recessives dominant, and being rare does
not make dominant ones recessive.  They refer specifically to two of the
several ways that alleles react in combination with each other.  For
instance, most forms of albinism are recessives, no matter how common
they are in any population because in combination with other alleles the
kits won't have the appearance of albinos.  There are some rare dominant
types of albinism, though, so then just one allele can cause the albinism
to be expressed.  Alleles can interact in a number of ways.  What is seen
may be between the two, or only one allele's influence may be seen, or
sometimes the result can actually be beyond the usual expression of the
alleles.
 
Melissa and Linda are right!  We will NOT be able to breed out deafness.
We can reduce the rate but actually removing any allele from a population
is actually difficult and having variable expression only makes it that
much harder.  Variable expression allows a genetic allele to hide.  It
is going to be harder to return to a point where there are few ferrets
having neural crest genetics than it was to get to a point where they are
as sadly common as they are in the U.S.  Some messes just do not have
good exit strategies so caution is needed beforehand.  It is not too late
for other nations to learn from this mistake in the U.S.  while their
own rates of neural crest genetic variants are low.  As for us in the
U.S., well, we have a long and painful slog ahead of us in trying to
first get breeders to be more careful and working bit by bit to try to
preferentially breed those not showing signs of neural crest variations
while hoping they don't just have them hidden.  It's mess, and it was
an avoidable mess.
 
Stephenie writes:
>He would leave the nest when old enough and would mate with a ferret
>from another nest; the gene would then be filtered out.
 
Nope.  If it was recessive to whatever what inherited from the mate it
would just be hidden below whatever dominant genetics came from the mate.
Remember the the genetics for sickle cell is not terribly unusual among
some Mediterranean and African peoples.  It is fatal if inherited in dual
form, though these days there are treatments.  Yet it persists because
if the person inherits only once copy then the disease does not present
itself.  This turns out to be a fortunate combination because having a
single copy of the sickle cell allele reduces the individual's
vulnerability to malaria by a substantial amount.  Single copies can be
hidden away...
 
Even if what else is inherited for that locus (genetic location) to go
along with the allele isn't dominant to it there is still the matter of
variable expression which also makes it hard to spot some individuals
with these alleles.  It is variable expression which causes some of these
animals to be deaf and other not deaf.  This varies among individuals.
The allele simple had different degrees and types of expression in
different individuals.  What is changes by neural crest variants is a
type of protocell which later leads to a number of cell types so you
can see why the effects are widespread and varied.
[Posted in FML issue 4669]