Transcript Gouldian Genetics - Gouldians Galore

Gouldian Finch Genetics
An introduction to:
Head, Breast & Body color
mutations and their patterns of
inheritance.
© Gouldians Galore 2009
Useful Genetics Terms
Trait: A trait is a physical characteristic that
can be inherited (e.g., head color).
Gene: You can think of a gene as a
segment of a chromosome that contains
the “recipe” for a specific trait.
Chromosome: A chromosome is a single
piece of coiled DNA which contains
multiple genes
Allele: An allele is one or more different
varieties of a single gene which can affect
the trait differently (e.g., Purple vs. Lilac vs.
White Breast)
Useful Genetic Terms
Phenotype: This is the observable trait of an
organism (e.g., Red Head)
Genotype: This is the actual genetic make up of
the bird which produces its phenotype.
Double-Factor: Double-Factor (simplified DF)
indicates that the bird is homozygous for a trait.
i.e., the bird has two of the same alleles.
Single-Factor: Single factor (simplified SF) means
just the opposite - the bird has only one of the
genes corresponding to a particular trait. It can
also mean the bird is heterozygous for a trait; i.e.,
it has different alleles (usually one dominant, one
recessive).
Useful Genetics Terms
Sex-Linked: When a trait is sex-linked, it
means the genes appear only on the sex
chromosomes.
In birds, the sex chromosomes are labeled
“Z” and “W,” where males are genetically “Z
Z” and females are genetically “Z W.”
In Gouldian Genetics, “sex-linked” always
refers to genes located on the “Z” sex
chromosome(s).
Useful Genetics Terms
Autosomal Traits: Autosomal traits are
those that are located on chromosomes
other than the sex chromosomes.
Dominant Trait: A dominant trait is one that
will be visually expressed if at least one
dominant allele is present.
Recessive Trait: The opposite of a
dominant trait, a recessive trait is one that
will only be phenotypically expressed if
both recessive alleles are present.
Head Color
Gouldian Finches come in three head
colors: Red, Black and Orange.
RH Male
BH Male
OH Male
Head Color
RH Hen (w/pins)
BH Hen
OH Hen*
*Photo courtesy Lainey
Alexander of Grasslands
Gouldians
Head Color
The color red is a sex-linked dominant
allele
The color black is sex-linked
recessive allele
The color orange is autosomal
recessive
Again, a sex-linked gene is one that is
located on the Z sex chromosome(s).
Red & Black Head Color
Red and Black head color are controlled by
the same gene and can be understood as
two “alleles” (varieties) of this gene.
Because this gene is sex linked, males can
either be “single factor” or “double factor”
for each, whereas females can only ever
be “SF” for red or “SF” for black. If you
remember that females are ZW and males
are ZZ, this makes sense.
Black and Red Head Color
So – genetically, the possibilities for the
sex linked head colors are as follows:
Where R = Red Allele
and r = Black Allele
DF Red Head Male (R, R)
SF Red Head Male (R, r)
DF Black Head Male (r, r)
SF Red Head Hen (R, W)
SF Black Head Hen (r, W)
Orange Head Color
When the discussion turns to Yellow, aka
Orange Head, things can become
confusing. Because this head color is
commonly referred to as “Orange,” due
how it appears visually, but also called
“Yellow,” depending on who you talk to, it is
difficult to ascertain the proper
nomenclature to use. To avoid confusion
with the “Yellow” Body Mutation, I will refer
to this head color as “Orange” for this
discussion.
Orange Head
Orange head is an autosomal recessive
gene. This means the gene is not located
on the sex chromosome(s), and because it
is recessive, requires both copies of the
gene be inherited in order for the bird to be
visually Orange Headed.
If a bird only possesses one copy of the
orange head gene, it is considered “split”
for Orange Head. It is not possible to
visually distinguish a bird that is split for
orange head from one that is not.
Orange Head
Note, however, that birds will only
display the orange head if they have
both copies of the recessive gene
and have at least one copy of the
dominant sex-linked red head
allele.
Orange Head
If a bird is genetically Black Head and
also carries both copies of the
recessive orange head gene, they will
be visually BLACK head with an
orange tipped beak and be deemed
“BH (OTB).”
BH (OTB)
This happens because the bird is still
genetically Orange head, but is
unable to express it due to only
possessing Black head alleles.
Although it can not produce Orange
Head feathers, it still expresses the
orange color through the beak, and
this is why they are “Orange Tip
Beak.”
BH (OTB)
The following photos illustrate BH (OTB) birds. Photos generously supplied by Lainey
Alexander (BH OTB Males) and Misty LaRue (BH OTB Hens).
BH OTB Males
BH OTB Hen
Orange Head
Because both cocks and hens can be “SF”
or “DF” for OH, the following genetic
possibilities exist:
R/R o = DF Red Head/Orange Head Cock
R/r o = SF Red Head/Orange Head Cock
(Essentially RH/BH/OH)
r/r o = Black Head/Orange Head Cock
R/R o o = Orange Head Cock
R/r o o = Orange Head/Black Head Cock
r/r o o = BH (OTB) Cock
Orange Head
R o = Red Head/Orange Head Hen
r o = BH/Orange Head Hen
R o o = Orange Head Hen
r o o = BH (OTB) Hen
Because hens can only be SF red or SF
black, you can see that unlike cocks, hens
can never be “triply split” for head color.
I.e., you will never see a “RH/BH/OH” Hen.
Head Color
Some body colors affect the head colors in the way
they visually appear.
For instance, the presence of the yellow body gene
affects the color black. Black Head birds will
appear charcoal grey to off-white in color if they
possess the yellow body gene.
The blue body gene affects the colors red and
orange, transforming these head colors to a
salmon to beige color.
c/o Misty LaRue
Questions?
Any questions so far?
Breast Color Genetics
Breast color, like Head color, comes in
three recognized varieties:
Purple, Lilac and White
Breast Colors
Breast color is controlled by a single
autosomal gene which comes in three
different varieties (alleles).
This means no bird, male or female,
can ever be triply split for the three
breast colors (there is genetically no
such thing as a purple split for lilac
split for white breast bird).
Breast Color
When it comes to dominance, breast
color works as follows:
Purple is dominant to Lilac and White.
Lilac is recessive to Purple but dominant
to White
White is recessive to both Purple and
Lilac.
Breast Color
This means that a visually Purple breasted
bird can be (potentially) genetically any one
of the following
Purple/Purple (or “DF Purple” - carrying two
purple alleles
Purple/Lilac (One purple allele, one Lilac
allele), or
Purple/White (One purple allele, one white
allele)
Like other splits previously discussed,
there is no reliable visual way of
distinguishing these splits from one
another.
Breast Color
With a Lilac breasted bird, the bird will either be
DF Lilac (two Lilac alleles) or Lilac/White.
Lilac comes in varying “shades,” from a pale
rose color, to a vibrant, more literal, Lilac shade.
These photos illustrate the variety of LB males.
Breast Color
With a White breasted bird, the only
possibility is for the bird to be
White/White (two copies of the white
allele) and express the White Breast.
Questions?
Any questions so far?
Body Color Genetics
Breeding Gouldians in captivity has
produced some interesting genetic
mutations to the “normal” Wild Type
Gouldian.
These mutations work by essentially
controlling the underlying pigments
associated with a “normal” Gouldian’s
colors.
Body Color Genetics
There are five commonly bred body
color mutations in Gouldians:
Dilute Males (1)
Yellow Males and Females (2)
Blue Body (3)
Pastel Blue Males (4)
Silver Body (5)
Body Color Genetics
Before continuing; note that there
exists different nomenclature for the
mutations between continents. To
avoid confusion, I will use the
nomenclature I find to be consistent
with U.S. Aviculture.
The Yellow Gene
The “yellow gene” is responsible for the
following mutations:
Dilute
Yellow
Pastel Blue (partially)
Yellow is a sex-linked mutation located on the
Z chromosome, so males are capable of
inheriting up to two copies, while females
can only ever inherit one.
The Yellow Gene
Yellow is understood to be “incompletely
dominant” to the normal green body color.
Incomplete dominance results when two
genes “combine” to create a visual
“intermediate.” Consider the following:
Pea plants are capable of producing flowers
that are Red (RR) or White (ww). However
– if a Red pea plant is crossed with a White
pea plant, the colors “combine” in the
heterozygote (Rw) – creating a flower that
is neither Red, nor White, but Pink.
Dilute Body
Adding the Yellow mutation to a Normal
Gouldian male produces a similar result.
Yellow is sex-linked, so males have the ability
to inherit either one or two copies.
When one copy is inherited, and the bird is
Purple Breast, we see the incomplete
dominance take effect.
The single yellow gene “competes” with the
remaining genes responsible for normal
green body, and the bird becomes an
intermediate mixture of yellow and green,
appearing “Diluted” when compared to a
normal Gouldian.
Dilute Body
Similar to Lilac Breast, Dilute birds
exist in a wide range of shades where
a varying degree of yellow is shown –
from a light Lemon Lime all the way to
a barely “Diluted” Lime Green body
color.
Dilute Body
Two BH Dilute Juveniles – the juvenile in the foreground is just
heading into his first molt.
Dilute Body
Dilute Gouldians
“SF Yellow”
What happens if a male inherits a single copy
of the Yellow gene, but he is not PB?
Due to an underlying correlation between
Lilac and White breast color and the yellow
body color gene, visually Lilac or WB
males that inherit even a single copy of the
yellow gene will be visually yellow in body
color, not Dilute.
For this reason, they are often called “Single
Factor Yellow” males, as they inherited a
“Single” copy of the gene, and they are
visually “Yellow” in body color.
SF Yellow
A question often asked
revolves around
distinguishing SF Yellow
males from “DF Yellow”
males. A few tricks involve
noting the turquoise band
behind the mask of the bird
and how bright it is. On a
SF Yellow – such as this
bird – it will be brighter blue.
Also, the normally black bib
under the beak will appear
a more grey color, whereas
on a DF Yellow male the bib
will be almost completely
white and the Turquoise
band more of an opalescent
color.
Yellow Hens
Females can never be dilute. This is because
they are only capable of inheriting a single
yellow gene (Z^y W), and thus the single
copy completely masks the expression of
the genes responsible for green body color,
and they appear yellow as a result.
For this reason, as well, it is redundant to say
a female is “SF Yellow,” and also
impossible for a female to ever be “DF
Yellow.”
Yellow Hens
RH PB Yellow Hen
“DF Yellow”
A male that inherits two copies of the
yellow gene, regardless of his breast
color, will be visually yellow.
This is because the presence of two
yellow genes completely overrides the
genes responsible for green body
color – resulting in a bright yellow
bird.
DF Yellow Male
RH PB DF Yellow Male
Blue Body
The “Blue Gene” is responsible for the
following mutations:
Blue
Pastel Blue (in part)
Silver (in part)
Blue is an autosomal recessive mutation
which means that it is not inherited on the
sex chromosomes. This also means that
both males and females can be either SF
or DF for the gene, but will only express it if
they are DF.
Blue Body
A RH, PB Blue Male
Blue Body
A BH, PB Blue Hen
Blue Body
We will address the different
variations of Blue Body – Pastel Blue
and Silver, separately.
In order for a bird to appear Blue, it
must inherit both copies of the Blue
Gene and also be genetically “normal”
– meaning, no mutated genes (i.e.,
Yellow) exist on the sex
chromosomes.
Blue Body
Because Blue Body is recessive, a bird can
inherit a single copy and be “Split” for Blue.
There is no reliable visual way to distinguish
split to blues from regular normal birds.
So, the genetic possibilities are as follows:
Normal + b = Normal/Blue Bird
Normal + bb = Blue Bodied Bird
Pastel Blue Males
Pastel Blue is the result of combining
the Yellow and Blue genes together.
Pastel Blues are Blue birds that are
also SF Yellow. They will always have
a Purple Breast.
You can think of it as being similar to
Dilute birds.
Pastel Blue
The presence of the single yellow gene “subdues”
the brilliance of a normal Blue bodied bird,
transforming it into to that of a light, powder blue
gray color instead.
The genetics of a Pastel Blue Male are as follows:
SF Yellow + Blue Body + Purple Breast
Again, because females can only be SF for Yellow
(causing complete expression), only males can
ever be Pastel Blue.
Pastel Blue
A RH PB Pastel Blue Male
Silver Body Males
There are two types of Silver Bodied
males:
Silver (SF Yellow) + White or Lilac
Breast
And
Silver (DF Yellow) + Any Breast Color
Silver (SF Yellow) Males
When a male that would ordinarily be Pastel Blue does not have
a Purple Breast, but is instead Lilac or White Breast, he
becomes visually Silver in body color instead. This is similar
to why a SF Yellow WB bird appears Yellow instead of Dilute.
Photo graciously supplied by Misty LaRue.
Silver (DF Yellow) Males
A Blue bodied male that is also DF
Yellow will always appear visually
Silver in body color regardless of the
color of his breast.
Silver (DF Yellow) Males
Juvenile RH PB Silver (DF Yellow) Male
Silver Body Hens
Because females can only be SF for
Yellow and express it, a Blue Bodied
hen that also possesses the Yellow
gene will appear visually Silver in
body color regardless of her breast
color.
Silver Hens
RH PB Silver Hen
Silver Body
So, the genetic possibilities for Silver Body
are as follows:
SF Yellow + White or Lilac Breast +Blue Body
Male
DF Yellow + Any Breast Color + Blue Body
Male
Yellow + Blue Body Hen
“All White” Silver Gouldians
Creating an “all white” Gouldian can be
accomplished by producing a Silver bird
that is also Black Head and White Breast.
This is because the Yellow gene transforms
the Black Head color into a Charcoal Grey
to White Color. (SF Yellow males will have
a grey colored head, whereas DF Yellow
Males and Yellow hens will have a nearly
white colored head instead)
“All White” Silver Gouldians
BH WB Silver Hen
Questions?
Any questions?
THE END
Thank you to Lainey Alexander and
Misty LaRue for providing additional
photos.
Dictionary.com and Wikipedia used to
paraphrase genetics definitions.