MONOHYBRID CROSS
1. Cross a homozygous dominant (TT) individual with a homozygous recessive (tt) individual.
Genotype Ratio ______________________________________________
Phenotype Ratio ______________________________________________
2. Cross a homozygous dominant (TT) individual with a heterozygous (Tt) individual.
Genotype Ratio ______________________________________________
Phenotype Ratio ______________________________________________
3. Cross two heterozygous individuals (Tt).
Genotype Ratio ______________________________________________
Phenotype Ratio ______________________________________________
DIHYBRID CROSS
Example #1: Cross two individuals who are both heterozygous tall (Tt) and red (Rr). The recessive
traits are short (t) and yellow (r).
Genotype Ratio __________________________________________________________________
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Phenotype Ratio _________________________________________________________________
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Example #2: In pea plants, purple (P) is dominant to white (p) and tall (T) and dominant to short (t). A
white short plant (pptt) is crossed with a plant that is heterozygous for both traits (PpTt).
Genotype Ratio __________________________________________________________________
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Phenotype Ratio _________________________________________________________________
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Example #3: In humans, brown eyes are dominant (B) to blue eyes (b) and brown hair is dominant
(H) to blond hair (h). Cross a homozygous dominant brown-eyed, blonde hair man (BBhh) with a
blue-eyed, heterozygous brown haired woman (bbHh)
Genotype Ratio __________________________________________________________________
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Phenotype Ratio _________________________________________________________________
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