Parrotlet Color Mutation Genetics

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Recessive mutations demonstrated using Punnett's Square
Each bird donates one set of chromosomes expressed with capital letters to demonstrate dominance. Recessive mutations are expressed with lower case letters. In this example "B" = blue so a normal bird not having any blue genes is expressed as "BB". A blue bird is expressed as "bb". A split bird is expressed as "Bb" denoting one blue gene.

Single Mutations - the following examples are valid for working with any autosomal recessive mutation. Although the blue mutation has been used in these examples, these Punnett Squares will apply to Blue, American Yellow, Pastel (European Yellow), Lutino, or Fallow.

	b	b
B	Bb	Bb
B	Bb	Bb

Blue (bb) to Normal Green (BB)
Results:
100% green/split blue (Bb)

	b	b
B	Bb	Bb
b	bb	bb

Blue (bb) to split blue (Bb)
Results:
50% visual blue (bb)
50% green/split blue (Bb)

	B	b
B	BB	Bb
b	Bb	bb

Split blue (Bb) to split blue (Bb)
Results:
25% normal green (BB) **
50% green/split blue (Bb) **
25% visual blue (bb)

** It is not possible to visually determine a normal from a split, they must be test bred

	B	b
B	BB	Bb
B	BB	Bb

Split blue (Bb) to normal green (BB)
Results:
50% normal green (BB) **
50% green/split blue (Bb) **

** It is not possible to visually determine a normal from a split, they must be test bred

Double Mutations - the following examples are valid for working with any two autosomal recessive mutations. These Punnett Squares will apply to any combination of Blue, American Yellow, Pastel (European Yellow), Lutino, or Fallow.

	bY	bY
By	Bb Yy	Bb Yy
By	Bb Yy	Bb Yy

Blue (bbYY) to Yellow (BByy)
Results:
100% green/split blue & yellow (BbYy) (double split)

	BY	By	bY	by
BY	BB YY	BB Yy	Bb YY	Bb Yy
By	BB yY	BB yy	Bb yY	Bb yy
bY	bB YY	bB Yy	bb YY	bb Yy
by	bB yY	bB yy	bb yY	bb yy

Double split (BbYy) (blue & yellow) to double split (BbYy) (blue & yellow)
Results:
6.25% normal green (BBYY) **
12.5 normal green/split yellow (BByY) **
12.5 normal green/split blue (bBYY) **
25% normal green/split yellow & blue (BbYy) (double split) **
6.25% Yellow (BByy) **
12.5% Yellow/split blue (bByy) **
6.25% Blue (bbYY) **
12.5% Blue/split yellow (bbYy) **
6.25% White (bbyy)

** It is not possible to visually determine whether any bird is a split, they must be test bred

	by	by
bY	bb Yy	bb Yy
bY	bb Yy	bb Yy

White (bbyy) to Blue (bbYY)
Results:
100% blue/split yellow (bbYy)