Panda Shepherd(what do you think?) - Page 14

"Panda x panda breedings should ordinarily produce ~25% panda homozygotes overall, so this is statistically significant and leads to the conclusion that panda is lethal in the homozygous form."

Pod,
For those of us that don't speak "genetic", could you put that in layman's terms?

An organism is homozygous for a particular gene when identical alleles of the gene are present on both homologous chromosomes.  Mutations often create null or absent alleles.  I read a report once that showed the American Blood Bank could not match children to mothers because of null alleles.

An individual that is homozygous recessive for a particular trait carries two copies of the allele that codes for the recessive trait. This allele, often called the "recessive allele" is usually represented by the lowercase form of the letter used for the corresponding dominant trait (such as, with reference to the example above, "p" for white flowers, which are recessive in pea plants). The genotype of an organism that is homozygous recessive for a particular trait is represented by a doubling of the appropriate letter, such as "pp".

I learned a lot about DNA from litigation.  Mutations, alleles, and recessive traits often defy logic and man's desire to control it.  I read his note and I believe what he is saying is that you can't breed Pandas with any level of success since the basic result is recessive.  While one could argue that there is enough dominant alleles to make it work laws of average tell you that you are dealing with mutts.

I could be wrong but I again state that I would fix the animal and make it a pet.  I saw an ad for one of these puppies for $700!  Who would sell a dog that is unknown to the world for that amount?  Wow

GSDJUstice, I am quite fluent in 'genetic', having taught highschool biology, but that post confused ME!

Okay, without looking it up, I believe dogs have 46 chromosomes. The chromosomes come in pairs, so that's actually 23 pairs.

The chromosomes are identified by number. I think the geneticist said the panda mutation occured on the 21st chromosome.

The gene that produces the panda colour is dominant. There only has to be one copy of it on one of the two 21st chromosomes for the colour to appear. If it were recessive, both chromosomes would have to carry the panda gene.

Te different forms of a gene are called alleles. Dominant alleles are represented by upper case letters, recessive by lower case. If both alleles are the same, the animal is HOMOZYGOUS for that trait. If the alleles are different (one panda gene, and one gene for 'normal' colour), the animal is HETEROZYGOUS.

So far all pandas have been heterozygous.  So, we cross two pandas: Pp x Pp. The alleles separate when the gametes (spern and egg) are formed, so, statistically, we will get 25%  of the offspring homozygous for panda (PP),  50% heterozygous (Pp) and 25% non-panda (pp)  See here for how to do this cross using a Punnett square: http://www.changbioscience.com/genetics/punnett.html

Some mutations are lethal in their homozygous form. There are various degrees of lethality. In the most severe cases, the embryo will not develop at all. In less severe cases, the embryo may abort, or be born with severe deformities, and die shortly after birth.

PM  I did ask Dr Neff for the actual numbers of panda and non panda pups born to panda x panda breedings, but didn't get an answer to that, just that there have been several litters and no double pandas have been identified by DNA.  Sunsilver has explained how the 25% should have occurred.

To make their results statistically significant, there must have been a large enough number of puppies born from these panda x panda breeding to assume that the absense of mutation homozygotes (double pandas) was down to a cause other than coincidence.

Justice, I did also ask about the probability of health issues, in particular hearing defects.  The answer was that as ~75 pandas have now been born, with no health issues, they can be reasonably confident that they will not occur.

My point was that, as melanocyte migration is somewhat random, more extensive white areas on the facial region could possibly occur, and if we look at the original panda - Frankie, it is evident that this gene appears to have the same effect as the S locus in that missing pigment in the eye region results in blue iris.  It is therefore resonable to assume that missing pigment in  the inner ear, if it were to occur in a panda, would results in hearing defects.  Not a major concern though, I would think, as the incidence, even if it did occur, would be very low.

 I read his note and I believe what he is saying is that you can't breed Pandas with any level of success since the basic result is recessive. While one could argue that there is enough dominant alleles to make it work laws of average tell you that you are dealing with mutts.


Justice, I really don't get what you mean by this.  could you expand a little more please.

duplicate post - oops!

Sunsiver, I haven't heard of any cases of lethal merle or white (S locus), only deformities ranging from slight to severe.  If you have any refs I'd be interested to read.

ETA: And as far as I know heterozygous M X M breeding produce the expected 1:2:1 ratio

You're right, Pod. Guess I was thinking of the lethal white gene in overo paint horses!

Sorry, shoulld have checked my info more thoroughly before posting that!

Here is info on the defects caused by merle, which may or may not be lethal:  www.geocities.com/Dimonde_Pomeranians/MerleFreePoms.html

Nothing scientific to add here but I have an interesting story.  This is my dog Abbie.  She is almost 12.  I got her from a gentleman who bred shepards in WV in the US.  She was the only dog that he everr got with her markings and gave her away because he thought she was "deformed" in some way.  She has been the BEST dog I have ever owned.  Soooo smart and loyal.  She has an amazing judge of character and zero tolerence for anyone who was drunk or loud. Energetic, loved ball and frisby.  We traveled all over together.  I was a raft guide for a time and she was great protection.  Never aggressive but stood her ground when needed.  In her old age she has slowed way down.  Loves sleeping on her mat and stealing food from my toddlers.  I thought for a longtime she was just a freak of nature.  I had NEVER seen another dog like her.  That or I thought the guy had lied and she was a mix.  I got her in WV she could be part chicken for all I knew! :) Today my sister calls and says "&*$*%$  there is a dog in my vet clinic and the owner says it is a "Panda Sheperd...the women saw Abbie's picture and wants to send you a swab so she can get her a DNA test to see if she is one too."   I about fell on the floor.  I immediately googled "Panda Shepard" and there was her image right there, I almost cried.  Abbie has cancer and probably will not make it to christmas.  SHe has been my closest most devoted friend.  Knowing that there is a possibility to maybe find another dog like her some day is amazing.  I will never replace her, I would never try she is one in a million.  But, to know that her temperment and traits can be had again helps with the hurt.  Reading the bitter nasty insulting comments about other peoples pets vexes and saddens me.  Regardless of your belief in "Pandas" or denial, know that people love their animals.  You can debate without the hurt.  Thank you for posting/reading my message.