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ktvd13 ktvd13
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10 years ago
In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele YY. Budgies that are homozygous for the recessive yy allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele BB directs synthesis of a blue pigment. Recessive homozygotes with the bbbb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

Determine the possible genotypes for green, yellow, blue, and albino budgies
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wrote...
10 years ago
You may have to start by constructing a Punnett Square.
wrote...
9 years ago
Blue: yyBB, yyBb
yellow: Yybb, YYbb
Green: YYBB, YyBb, YYBb, YyBB
Albino: yybb
wrote...
Staff Member
9 years ago
Purebred Green - YYBB, YyBB, YYBb, YyBb

(In order for the parent to have green feathers, it must have at least one dominant allele for each gene - YY or Yy for yellow and BB or Bb for blue. A green Budgie could have any combination of these, giving the four possible genotypes listed above.)

Purebred Albino - ONLY yybb

The only way to get no pigment on the yellow feathers locus is to have yy, and the only way to have no pigment on the blue feathers locus is to have bb. Therefore, the only possible combination for an albino budgie is yybb. (Note, this phenotype is controlled by a homozygous genotype)
- Master of Science in Biology
- Bachelor of Science
wrote...
9 years ago
Follow-up Question 1:

A cross is made between a pure-breeding green budgie and a pure-breeding albino budgie. What are the genotypes of the parent birds?
wrote...
Staff Member
9 years ago
Purebred Green - YYBB, YyBB, YYBb, YyBb

(In order for the parent to have green feathers, it must have at least one dominant allele for each gene - YY or Yy for yellow and BB or Bb for blue. A green Budgie could have any combination of these, giving the four possible genotypes listed above.)

Purebred Albino - ONLY yybb

The only way to get no pigment on the yellow feathers locus is to have yy, and the only way to have no pigment on the blue feathers locus is to have bb. Therefore, the only possible combination for an albino budgie is yybb. (Note, this phenotype is controlled by a homozygous genotype)

yybb X YYBB
- Master of Science in Biology
- Bachelor of Science
wrote...
Staff Member
9 years ago
Green buldgie - YYBB or YyBb or YyBB or YYBb

Albino buldgie - yybb
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