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GENETICS
CAN BE FUN
....POSTSCRIPT
ANSWER
by Dr. Bruce M. Cattanach
In a series of six articles
published in Dog World over a number of years, I have described the
introduction of a dominantly inherited bobtail gene into the Boxer to
produce an undocked dog with a naturally short tail. This was achieved
by repeated backcrossing to Boxer after an initial cross to a bobtail
Pembroke Welsh Corgi. In the course of this work, a molecular genetic
study was also conducted and this identified the bobtail gene itself at
the DNA level. Essential to the identification was a co-occurrence of
the bobtail effect with the DNA change identified. There was however a
problem.
The problem:
As described in a postscript
to the last article (Part 6) one apparent exception to the co-occurrence
of the tail effect and DNA change was found. A bitch that was thought to
have a bobtail did NOT in fact carry the changed DNA thought to
represent the bobtail gene mutation. On re-examination, however, this
abnormal tail was found to have a kinked bony structure unlike the
bobtail with its typical "fatty" distal pad and profusely
hair-covered filament at the tip. Instead, it closely resembled the
"screw tails" that occur occasionally in perhaps all
long-tailed breeds. Therefore, was this abnormal tail attributable to a
chance, non-inherited screw tail effect rather than to the bobtail gene?
Insofar as the answer was essential to correct identification of the
gene, it was necessary to resolve this issue. This could be done by
test-mating the bitch to determine if the tail effect was inherited or
not. If it was not inherited, the bobtail gene was not involved and the
bitch would not be expected to have the bobtail gene.
The
"screw tail" bitch; fourth generation from Corgi.
This article describes the
test-mating and the results obtained. But in constructing the test it
seemed worthwhile asking a further question of more general breeder
interest. Would any Corgi-type characteristics (short legs, long coat,
etc.) reappear if one inbred on Corgi in addition to testing for the
bobtail gene?
The approach:
The screw-tailed bitch was
from the fourth generation of crossing and looked typically Boxer. To
test if she would transmit the tail effect to her progeny, she was mated
to a normal tailed dog.
The long tailed dog used for stud,
also fourth generation.
And, to answer the question
on the possibility of Corgi characteristics reappearing in her progeny
if one "doubled up" on Corgi, she was mated to dog that, like
her, was only four generations removed from Corgi. He too looked a
fairly good Boxer.
Pup from the "double" Corgi
litter.
The answers:
1. Was the abnormal tail
inherited?
The abnormal tailed bitch
produced seven puppies and all had perfectly normal long tails. If the
tail abnormality was due to the bobtail gene, half the pups on average
should have had some form of bobtail.
Litter from screw tail bitch; all long
tails.
However, based on the 50:50
expectation, the chances of no abnormal tailed pups being produced among
seven born is less than one in a hundred. It may therefore be concluded
that it is extremely unlikely that the exceptional bitch carried the
bob-tail gene and, accordingly, the molecular identification of the
bobtail gene is validated. The abnormal tail can best be ascribed to one
of those rare non-inherited developmental anomalies that are found when
one breeds animals. Several examples of this type of tail have in fact
been noted in Boxers over recent years.
2. Could Corgi
characteristics reappear on inbreeding?
All seven pups looked
typically Boxer at birth, but health problems limited the study. The
bitch required a caesarian (as had her Boxer mother before her), the
stitching broke down, and infection set in. This necessitated her return
to the vets for re-anesthesia, re-stitching and antibiotic treatment.
The bitch was quite ill, she lost her milk for a few days and, despite
all efforts, three of the seven pups
faded. A mere four pups is not very informative but, at about 6 weeks,
all looked typical Boxer puppies. All were short backed, and had decent
heads with obvious Boxer chins. Certainly none showed any trace of the
short legs and longer coat type of the Corgi, in complete accord with
genetic expectation based on the established inheritance of these
characteristics.
Four surviving puppies from the
"double" Corgi litter.
Where are we now?
The investigative parts of
this bobtail project are now complete, although bobtail x bobtail test-matings
will be conducted in some later generation/s. The key question that
remains is breeder attitude to the bobtail as an alternative to docking
in the event of a complete docking ban. For the present, there is
limited interest in the UK although one major breeder is now highly
enthusiastic about bobtail Boxers and intends to introduce the gene into
her kennel. A few smaller kennels are also interested as a means of
reducing the need for docking. The main interest in the bobtail,
however, is developing abroad - in countries where docking has been
banned.
The bobtail male, Steynmere
Hot Shot, that I sent to Norway has created much interest there. Indeed,
an article centered around the dog has recently been published in a
major Norwegian dog magazine, Hundesport, and has even aroused interest
in the bobtail among breeders of other traditionally docked breeds. Hot
Shot is being used at stud in Finland, Sweden, and Holland, as well as
in Norway, and breeders have been impressed by his first puppies. The
oldest caught attention recently with a remarkable fourth place in an
entry of thirteen youngsters - under a German specialist judge.
Steynmere Hot Shot, bobtail dog now in
Norway
Meanwhile an impressive Hot
Shot daughter, Steynmere Corona, with possibly two other bitches (one by
Santonoaks Red Hot Prospect and one by Barbarossa Matador Magic) and
also Corona’s brother, Steynmere Total Eclipse, will keep the bobtail
flag flying here in the UK.
Steynmere Corona, the key fifth
generation bitch (by Hot Shot) to carry on the line in the UK.
Steynmere Total Eclipse, littermate to
Corona.
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