Recessive Inheritance

If you've got dominant inheritance sorted out, recessive should be easy for you.

Recessive inheritance is very similar to dominant; the only thing that you need to know is that the bird will need both genes to make the mutation visible in their appearance (remember that dominant mutations need only one gene with the mutation for it to be visible). E.g. a budgie needs both genes with the recessive pied gene factor for it to be (visually) a Recessive Pied, but only one dominant pied gene is needed to make a (visually) Dominant Pied budgie.

Birds that have only one gene with a recessive mutation will appear no different from any bird that does not have the gene. However, they can still pass this gene to their offspring that might affect their appearance and so we say they are split for the recessive gene.

 R 

gene with recessive factor

r

normal gene


There are again only three, different (because rR is the same as Rr), combinations:

RR

recessive on both genes, so this bird appears recessive

rR

recessive on one gene, so this bird appears normal

rr

no recessive factor, so this bird also appears normal


Here are a few matings to give you a better idea of how recessive genes behave in the presence of normal genes:

RR x rr (visually recessive x normal)

Recessive x Normal

This pairing results in 100% rR (normal split recessive usually written normal/recessive). All of the offspring will appear normal, but everyone of them can pass on the recessive gene when they are paired.

Here's what happens when two normal/recessive birds are paired together.

rR x rR (normal/recessive x normal/recessive)

Normal/Recessive X Normal/Recessive

25%

rr

normal

25%

rR

normal/recessive

25%

Rr

normal/recessive

25%

RR

recessive/recessive - usually written simply as recessive


Or, combining the normal/recessive results:

25%

rr

normal

50%

rR

normal/recessive

25%

RR

recessive


The first two results produce normal-looking offspring, only the last results in birds that visually appear recessive.

In recessives, we don't talk about single and double factor birds as we do in dominant inheritance, but a split recessive (e.g. green split blue) is equivalent to a single factor (but just not visible when we look at the bird as it would be if the gene was dominant) and a bird with both recessive genes is equivalent to a double factor bird.

Breeding birds with recessive genes is harder than those with dominant mutations because it is not possible to tell which birds that appear normal are split for the recessive gene unless they originate from a mating where they could only be split recessive (e.g. as in the first example above).

To find out, test pairings are used where a suspected split recessive is paired with a recessive (which has both recessive genes) and if a recessive appears amongst the offspring you know that the bird is definitely split. However, if it does not produce any recessives this only means that it might not be split and that it might be that only its normal gene was passed on to its offspring and none got a copy of its recessive gene.

Greywing, Clearwing & Dilute

These three factors all lie on the same gene, this means that only one of them can exist on a chromosome – i.e., there is only one position on a chromosome that they can exist and if one of these factors has occupied it then the others cannot.

Hence, it is not possible to combine these three factors in one bird, as there are three factors and only two positions (remember, there are two chromosomes) they can occupy. More importantly, it is not possible to combine any of these factors visually, e.g. a Greywing Yellow is not possible (Yellow being the name given to green series Dilutes).

These three factors do have a rigid hierarchy with them being dominant and recessive relative to each other.

  • Greywing is dominant to Clearwing and to Dilute.

  • Clearwing is dominant to Dilute, but recessive to Greywing.

  • Dilute is recessive to Greywing and to Clearwing.

These rules have to be taken into account when breeding these factors together.

The following pairs should make it clearer:

Greywing x Clearwing

  

100%

  

Greywing/Clearwing

  

(Greywing is dominant to Clearwing)


 
 
   

Greywing/Clearwing x Clearwing

 

50%

 

Greywing/Clearwing

 

(Greywing is dominant to Clearwing)


 

50%

 

Clearwing

   

 
 
   

Greywing x Dilute

 

100%

 

Greywing/Dilute

 

(Greywing is dominant to Dilute)


 
 
   

Greywing/Clearwing x Dilute

 

50%

 

Greywing/Dilute

 

(Greywing is dominant to Dilute)


 

50%

 

Clearwing/Dilute

 

(Clearwing is dominant to Dilute)


 
 
   

Greywing/Dilute x Clearwing/Dilute

 

25%

 

Greywing/Clearwing

 

(Greywing is dominant to Clearwing)


 

25%

 

Greywing/Dilute

 

(Greywing is dominant to Dilute)


 

25%

 

Clearwing/Dilute

 

(Clearwing is dominant to Dilute)


 

25%

 

Dilute

   

Goldenface, Yellowface M1 & Yellowface M2

Many breeders will regard these factors as dominant and the terminology used is that of single-factors and double-factors, but they are actually believed (by people who have researched these varieties) to be different types of blue factor and, like Whiteface Blue, they are recessive to Green.

As so many people still refer to the mutations as single- or double –factors, here is a table showing the correspondence between recessive and dominant terminology.

Terminology

Recessive

 

Dominant

Whitefaced Blue/Whiteface Blue

 

Blue

Yellowface Blue M1/Whiteface Blue

 

Single-factor Yellowface M1

Yellowface Blue M1/Yellowface Blue M1

 

Double-factor Yellowface M1

Yellowface Blue M2/Whiteface Blue

 

Single-factor Yellowface M2

Yellowface Blue M2/Yellowface Blue M2

 

Double-factor Yellowface M2

Goldenface Blue/Whiteface Blue

 

Single-factor Goldenface

Goldenface Blue/Goldenface Blue

 

Double-factor Goldenface


The hierarchy of dominance between the three factors, Green and Whiteface Blue is:

Dominance

Most

 

Green


 

Goldenface Blue (Australian Yellowface)


 

Yellowface Blue Mutant 2


 

Yellowface Blue Mutant 1 (Creamface)

Least

 

Whiteface Blue


This means that a Green series bird can be split for any of these three factors, but cannot carry two factors, otherwise it would be a Blue series bird.

A Whitefaced Blue cannot be split for any yellowface blue factor, which is why many breeders regard their inheritance as being dominant – also since who can tell if a Green series bird is displaying a yellowface factor or not? However, a yellowface blue can be split for Whiteface Blue (using dominant inheritance terminology they are single-factors).

A Goldenface Blue can be split for either of the two yellowface blues or for Whiteface Blue, but only one at a time, e.g. Goldenface Blue/Yellowface Blue M1 or Goldenface Blue/Whiteface Blue.

Recessive Factors

The recessive factors that have occurred to date are:

Blackface

Blue

Brownwing*

Clearwing

Dilute

English Fallow

English Grey*

Faded

German Fallow

Goldenface Blue

Greywing

Mottled

Non-sex-linked Ino*

Recessive Pied (a.k.a. Danish Pied)

Saddleback

Scottish Fallow*

Yellowface Blue Mutant 1

Yellowface Blue Mutant 2

*May no longer exist. Does anyone know of anyone keeping these varieties?