You performed breeding experiments on a newly discovered species of unicorn. the
ID: 7357 • Letter: Y
Question
You performed breeding experiments on a newly discovered species of unicorn. the horns came in three colors: white, black and gray. A single gene controls color. When you crossed pure-breeding white-horned individuals with a pure-breeding black-horned ones, you got all gray-horned F1 offspring. You then crossed the gray-horned offspring with each other. In the F2 you got white-,gray- and black-horned offspring in a 1:2:1 ratio.a) What is the genetic mechanism behind the horn color of these unicorns?
b) Outline the crosses explained above, giving RATIOS, GENOTYPES, and PHENOTYPES of the P, F1, and F2. Use Punnet Squares to help determine.
Explanation / Answer
pure-breeding white-horned individuals x a pure-breeding black-horned ones
bb X BB
Bb------------ gray
Bb------------ gray x Bb------------ gray
B
b
B
BB black
Bb gray
b
Bb gray
bb white
In the F2 you got white-,gray- and black-horned offspring in a 1:2:1 ratio.
a) What is the genetic mechanism behind the horn color of these unicorns?
b---------recessive allele
B----------Dominant allele
BB –homozgous genotype is black
bb ------homozgous genotype is white
Bb –heterozygous - gray
BB black
Bb gray
Bb gray
bb white
B
b
B
BB black
Bb gray
b
Bb gray
bb white
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