Gouldian Finch Genetics

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.

Gouldian Finch Genetics