HEREDITY
MONOHYBRID CROSS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The couple will have a blue-eyed fourth child.
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The couple will have a brown-eyed fourth child.
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They have a 75% chance of having a blue-eyed child.
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They have a 25% chance of having a blue-eyed child.
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Detailed explanation-1: -Of these three genotypes, only bb, the homozygous recessive genotype, will produce a phenotype of blue eyes. The heterozygous genotype and the homozygous dominant genotype both will produce brown eyes, though only the heterozygous genotype can pass on the gene for blue eyes.
Detailed explanation-2: -For example, when someone has brown eyes, it doesn’t necessarily mean they have homozygous genes. It’s possible for them to have a combination, or “Bb”, having one dominant brown allele and one recessive blue allele.
Detailed explanation-3: -There is a 75% chance of a brown-eyed child, because both Bb (50% chance) and BB (25% chance) genotypes result in brown eye phenotype. There is a 25% chance of a blue-eyed child, because only a bb genotype results in a blue eye phenotype.
Detailed explanation-4: -In humans, the allele for brown eyes (B) is dominant. The allele for blue eyes (b) is recessive. If a woman with genotype BB and a man with a genotype Bb have four children.