Inheritance of coat and colour in the Griffon Bruxellois dog

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Inheritance of coat and colour in the Griffon Bruxellois

dog

R Robinson

To cite this version:

Note

Inheritance of

coat

and colour

in

the Griffon Bruxellois

_dog

R Robinson

St

_{Stephens Nursery,}

St

_{Stephens Road,}

London W13

_8HB,

UK

(Received

5

_July

1993;

accepted

12 November

₁₉₉₃₎

Summary - The varieties of the Griffon Bruxellois

_dog

consist of the colours

_black,

red and black and tan, combined with either a

rough

or normal coat.

_Analysis

of litter data reveals that the colours are

_{produced by}

mutant alleles of the

agouti locus,

solid black

(A

9

),

dominant

_yellow

_(A

_Y

₎

and black and tan

_(at),

_{respectively. Rough}

coat is inherited

as dominant to normal coat and may be attributed to the dominant wire hair mutant allele W h.

breed

_/

canine colours

_{/ dog}

genetics

Résumé - Hérédité du pelage et de la couleur du chien Griffon bruxellois. Les variétés du chien

_Griffon

bruxellois

correspondent

aux couleurs _{noir, rouge et noir et}

feu,

combinées avec un

_pelage

normal ou _grossier.

_L’analyse

de données de

portées

révèle que ces couleurs sont

_produites

_par des mutants au locus

_Agouti,

noir

_uniforme

_(A

_S

_),

_jaune

dominant

_(A

_Y

₎

et noir et

_feu

_(a

_t

₎

respectivement. Le

_pelage

grossier est dominant vis-à-vis du

_pelage

normal et _peut être attribué à l’allèle mutant

_poil

dur

_(Wh).

pelage / coloration

_{/ génétique}

canine

INTRODUCTION

It is

_important

to

_investigate

the inheritance of coat

_type

and colour varieties in individual breeds of

_dog.

It is

_possible

to make

_{generalizations}

to

_explain

the

heredity

in many breeds

_(Little,

1957;

Robinson,

1990)

but it is

_becoming

_apparent

that certain breeds possess mutant alleles which are

particular

to the breed. From the earliest

_days

of canine

_genetics,

it has been known that alleles

₍₁

dominant and 1

_recessive)

at 2

_independent

loci can

_produce

a similar

_yellow

or red coat

colour

_(Little,

_{1957; Robinson,}

_1990).

More

_recently,

it has been discovered that 2 alleles at the same locus can

_produce

a

_completely

black coat

_(Willis,

1976; Carver,

1984).

One can,

therefore,

no

longer

assume

(Little, 1957)

that black is

always

harlequin

pattern

of the Great Dane is

_genetically

different from the merle

pattern

of other

_breeds,

which it resembles

_{phenotypically}

_(Sponenberg,

_1985;

O’Sullivan

and

Robinson,

1989).

Tweed is another colour which resembles

merle,

but which is

genetically

different and

_unique

to the Australian

_{Shepherd dog}

_(Sponenberg

and

Lamoreux,

1985).

The

_{present report}

describes an

_analysis

of coat

_type

and colour varieties in the

Griffon

_Bruxellois,

a

_toy

breed of

_dog

(2.2-4.9 kgs),

which was

_developed

in

_Europe

towards the end of the 19th

_century.

The coat is bred for 2

_types:

that normal for the

_dog

_(known

as

smooth)

and a wire hair

(known

as

rough).

The 2 most

common colour varieties are the

_red,

which is

_usually,

if not

_always,

_accompanied

by

a variable black facial

mask,

and the solid black. A less common

_variety

is the

black and

_tan,

where the whole

_body

is black with tan-coloured

_markings.

These

comprise

2 tan

_patches

on the front of the

chest,

tan on the inside of the

legs,

and

on the front of the

_legs

from the

carpal

to the

_{hock, together}

with 2 characteristic small tan

_spots

above the _eyes.

MATERIALS AND METHODS

The

_{investigation}

_{proceeded by analysing}

coat

_quality

and colour for _pups in litters

reported

by

breeders for the years 1991 and 1992. In

total,

126 litters

comprising

349 _pups were

_examined;

of these 49 litters

_provided

evidence for

_segregation

of

mutant alleles as summarized in table I. The

_frequency

of

_phenotypes

represent-ing

the

_segregation

of the alleles was estimated

by

the a

_priori

method of

_Hogben

(see

Emery,

1976,

p

40-42)

on the

assumption

of near

complete

ascertainment. The

validity

of the method was checked

by

a

parallel

maximum likelihood estimation

of the

_probability

_(p)

for the recessive

_phenotype

within each

_mating

_type

_by

the method of Haldane

_(see

_Emery,

1976,

p

42-43).

The estimated values

of p

are tabu-lated in the last column of table I. These biometric

_procedures

_effectively

correct for the

_expectations

as observed

retrospectively,

due to absence of

_segregation

in small litters

_{composed entirely}

of the dominant

phenotype

from

_heterozygous

parents.

RESULTS

The

_heredity

of the

_rough

coat is that of

_segregation

of a dominant mutant

_allele,

as shown

_by

the first 3 entries of table I. The observed

_frequencies

for the intercross and backcross

_matings

are

fully

consistent with

_expectation,

as indicated

by

the

non-significant

values for

_x

₂

and p values in

agreement

with the

_{expectations.}

The

mating

of smooth to _{smooth gave 10} smooth-coated _pups.

The

_completely

black colour behaved as a

_monogenic

dominant to

red,

as

evidenced

_by

the 4th to 6th entries of table I. The observed

_frequencies

are in accord

with

_expectation,

as shown

_by

the

_{non-significant}

x2

and

_p values in

_agreement

with

the

_{expectations. Furthermore,}

the

_mating

of red to red gave 242 red pups.

The black and tan

_variety

is

_relatively

uncommon and this is reflected

by

the

small amount of data on the

_segregation

of the colour.

_However,

it is

_apparent

that

Segregation x

2

has 1

_degree

of freedom

_(each

of which is

_{non-significant);}

p:

probability

of the recessive

_phenotype

f se with

expected

value in brackets.

_Symbol

A of the last 3

_matings

_represents either of the

agouti

alleles AS or A’y

(see

text).

table

_I).

In table

I,

the litters from black and red

parents

that gave black and tan pups are

_grouped

since there were so few of each. The

_legitimacy

for this is

_given

in

the discussion. The black and tan colour behaves as a recessive to both black and red.

The mutant allele for chocolate colour is

_present

in the breed at a low

_frequency.

Two litters from black

_parents

_gave 7 black and 3 chocolate _pups. This indicates

monogenic

recessive

_heredity

and is in

_keeping

with

_breeding

information on the

colour for other breeds of

_dog

_(Little,

_{1957; Robinson,}

_1990).

DISCUSSION

A

_general

_exposition

of the nature and

_heredity

of coat and colour mutant alleles for the

_dog

_may be found in Little

₍₁₉₅₇₎

and Robinson

_(1990).

The

_monogenic

inheritance of the

_rough

coat found in the Griffon Bruxellois conforms with the dominant

_heredity

of the trait in several other breeds

_(Robinson,

1990).

On the

_principle

of _economy of

_hypothesis,

the same mutant allele _may be

involved,

with the

_proviso

_{that this may} not

_necessarily

be the case. The

_symbol

Wh denotes the wire hair allele

_{(Robinson, 1990).}

To

_comprehend

the nature of the colour varieties for the Griffon

_Bruxellois,

it is wise to review the relevant

_genetics

of the

_dog.

The solid black colour may be

produced

by

either of 2 alleles at the

agouti

locus. These are:

₁₎

dominant black

_{AS ;}

I

and

₂₎

_non-agouti

or recessive black a. The red colour _may be

produced by

either of

2 alleles:

₁₎

dominant

_yellow

_A

_y

_,

also at the

_{agouti locus;}

and

₂₎

non-extension of black or recessive

yellow

e at the extension locus. It is relevant that the e is

_epistatic

The solid black

_variety

of the Griffon Bruxellois is due to the AS allele

since,

if it were due to the a

allele,

it would be

incapable

of

_segregating

red and black and

tan. The red

_variety

is due to the Ay allele since if it were due to the e allele it

would be

_incapable

of

_segregating

black and tan.

Moreover,

there is another reason

for

_excluding

the e allele. The red

_variety

_habitually

has a black

mask,

which can

manifest in

_conjunction

with Ay but not with e.

The black and tan

_variety

is

_produced

_by

the

at since the colour

_segregated

from

mating

of both black to black and from red to

_red,

which is

_completely

consistent with its

_position

in the

_agouti

series as the most recessive allele.

Accordingly,

the

_genotypes

of the colour varieties of the Griffon Bruxellois _may be written as: solid black

A!-,

red Ay- and black and tan

_a

_t

_a

_t

_,

where the dash indicates

_possible

_homozygosity

or

_{heterozygosity}

of the allele. All of the colour

varieties _may be bred with or without the

rough

coat allele Wh.

The

_{investigation provided}

some information on the distribution of litter sizes for

the breed. The range varied from 1 to 6 _{pups per}

_litter,

with a mean of 2.71t0.13 _per

litter. The

_frequency

distribution was

_notably

skewed towards the smaller litters.

ACKNOWLEDGMENTS

I thank the many breeders who

provided

details of litters and

particularly

Mrs P

Sturman,

archivist of the Griffon Bruxellois

Club,

who collected the information that formed the basis of this

_study.

REFERENCES

Carver EA

₍₁₉₈₄₎

Coat colour

_genetics

of the German

_{shepherd dog.}

J Hered

_75,

247-253

Emery

AEH

₍₁₉₇₆₎

_Methodology

in Medical Genetics. Churchill

_Livingstone,

Edin-burgh

Little CC

₍₁₉₅₇₎

Inheritance

_of

Coat Colour in

_Dogs.

Cornell

_University

Press,

NY

O’Sullivan

N,

Robinson R

₍₁₉₈₉₎

_Harlequin

colour in the Great Dane

_dog.

Genetica

78,

215-218

Robinson R

₍₁₉₉₀₎

Genetics

_for

Dog

Breeders.

_{Pergamon Press,}

Oxford

Sponenberg

DP

₍₁₉₈₅₎

Inheritance of

_harlequin

color in Great Danes. J Hered

_76,

224-225

Sponenberg

DP,

Lamoreux ML

₍₁₉₈₅₎

Inheritance of tweed: a modification of merle

in the Australian

_shepherd

_dog.

J Hered

79,

303-304