Simple Genetics

The sex chromosomes in birds are Z and W – not X & Y as in mammals.

The male birds have two Z and Z sex chromosomes, and females have a Z and a W.

Male birds make sperm which always have a Z chromosome.

Female birds make gametes which can have either a Z or a W chromosome

• Male offspring get a Z chromosome from their father and a Z chromosome from their mother.
• Females get a Z chromosome from their father and a W chromosome from their mother
• Z chromosomes never pass from mother to daughter
• W chromosomes always pass from mother to daughter

Females have just one copy of the Z genes on the sex chromosomes.

Males have two copies of the Z genes, one on each sex chromosome

The W-chromosome is small with few genes.

• The Z-chromosome is large and has many sex-linked genes, including genes that control feather colour and colour intensity.

SEX LINKED
EG REDFACED PARROT FINCH

SEA GREEN MALE X SEA GREEN FEMALE
100% SEA GREEN

SEA GREEN MALE X NORMAL FEMALE
50% SPLIT MALE
50% SEA GREEN FEMALE

NORMAL MALE X SEA GREEN FEMALE
50% SPLIT MALE
50% NORMAL FEMALE

SPLIT MALE X SEA GREEN FEMALE
25% SPLIT MALE
25%SEA GREEN MALE
25% SEA GREEN FEMALE
25% NORMΑL FEMALE

SPLIT MALE X NORMAL FEMALE
25% SPLIT SEA GREEN MALE
25% NORMAL MALE
25% SEA GREEN FEMALE
25%, NORMAL FEMALE

RECESSIVE
EG GOULDIAN FINCH

WHITE BREASTED MALE X WHITE BREASTED FEMALE
100% WHITE BREASTED

WHITE BREASTED MALE X NORMAL FEMALE
100% SPLITS

NORMAL MALE X WHITE BREASTED FEMALE
100% SPLITS

SPLIT MALE X SPLIT FEMALE
25% WHITE BREASTED
50% SPLIT
25% NORMAL

SPLIT MALE X NORMAL FEMALE
50% SPLIT
50% NORMAL
SPLIT MALE X NORMAL FEMALE
50% SPLIT
50% NORMAL
DOMINANT MUTATION

DOUBLE FACTOR COCK X DOUBLE FACTOR HEN
100% DOUBLE FACTOR

DOUBLE FACTOR COCK X S1NGLE FACTOR HEN
25% DOUBLE FACTOR COCKS
25% SINGLE FACTOR COCKS
25% DOUBLE FACTOR HENS
25% SINGLE FACTOR HENS

DOUBLE FACTOR COCK X NORMAL HEN
50% SINGLE FACTOR COCKS
50% SINGLE FACTOR HENS

SINGLE FACTOR COCK X SINGLE FACTOR HEN
* 50% DOUBLE FACTOR COCKS
25% SINGLE FACTOR COCKS
25% NORMAL COCKS
50% DOUBLE FACTOR HENS
25% SINGLE FACTOR HENS
25% NORMAL HENS

SINGLE FACTOR COCK X NORMAL HEN
25% SINGLE FACTOR COCKS
25% NORMAL COCKS
25% SINGLE FACTOR HENS
25% NORMAL HENS