Modifications of dihybrid cross
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MODIFICATION OF DIHYBRID CROSS
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GENETIC EXPLANATION
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F2 PHENOTYPIC RATIO
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AABB
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AABb
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AaBB
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AaBb
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AAbb
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Aabb
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aaBB
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aaBb
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aabb
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Classical Dihybrid Ratio
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9
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3
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3
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1
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Complete dominance at one locus and Incomplete dominance at another locus (co-dominance)
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3
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6
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1
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2
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3
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1
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Complete dominance lacking at either locus (co-dominance at both locus)
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1
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2
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2
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4
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1
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2
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1
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2
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1
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Complete dominance at one locus and Homozygous dominant lethal at another locus
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6
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3
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2
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1
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Incomplete dominance at one locus (co-dominance) and Homozygous dominant lethal at another locus
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2
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4
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1
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2
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2
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1
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Homozygous recesive lethal at either locus
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1
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2
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2
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4
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Recessive Epistasis
When one gene is homozygous recessive, it hides the phenotype of the other gene.
( aa epistatic to B and b )
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9
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3
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4
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Dominant Epistasis
When one gene is dominant, it hides the phenotype of the other gene.
( A epistatic to B and b )
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12
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3
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1
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Dominant and Recessive Epistasis
When either gene is dominant, it hides the effects of the other gene.
( A epistatic to B and b, bb epistatic to A and a, A and bb produce identical phenotypes)
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13
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3
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Duplicate Recessive Epistasis
When either gene is homozygous recessive, it hides the effect of the other gene.
( aa epistatic to Bb, bb epistatic to A and a )
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9
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7
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Duplicate Dominant Epistasis
When either gene is dominant, it hides the effects of the other gene.
( A epistatic to B and b, B eptistatic to A and a )
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15
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1
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Duplicate Interaction
When either gene is dominant, it hides the effects of the other gene.
( A and B interact)
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9
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6
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1
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Last modified: Friday, 30 March 2012, 4:36 AM
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