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Difficulty: EasyGenetics and Heredity

In humans, the allele for having freckles (FF) is dominant over the allele for not having freckles (ff). If an individual inherits the heterozygous genotype FfFf, which physical characteristic will they display?

  1. A
    They will not have freckles because recessive traits are expressed more frequently in populations.
  2. B
    They will not have freckles because two copies of a dominant allele are required for expression.
  3. They will have freckles because a single dominant allele is sufficient to mask the recessive allele.Answer
  4. D
    They will show an intermediate blend because dominant and recessive alleles always mix equally.

Answer

They will have freckles because a single dominant allele is sufficient to mask the recessive allele.
Because the allele for freckles (FF) is dominant, an individual with the heterozygous genotype (FfFf) only needs one copy of the dominant allele to display freckles. The dominant allele completely masks the expression of the recessive allele (ff).

Step-by-Step Solution

1
Identify the relationship between the two alleles given in the problem.
The allele FF (freckles) is dominant, and ff (no freckles) is recessive.
Determining which allele is dominant establishes the rule of expression.
2
Determine the physical phenotype produced by the heterozygous genotype FfFf.
The organism expresses the dominant trait (having freckles).
In simple Mendelian inheritance, having at least one dominant allele results in the dominant phenotype.

Key Concept

Dominant vs. Recessive Allele Expression in Heterozygous Genotypes
Estimated Time:45s
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Topics

Genetics and Heredity

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