Freckles are small dark patterns visible on a person's face. The occurrence of freckles is caused by a dominant allele that can be denoted by the letter F. In contrast, the recessive allele that causes the individual not to have freckles can be denoted by the letter f.

The genome of a person with freckles is either FF (homozygous) or Ff (heterozygous). The notation Ff means that one homologous chromosome has the allele F, whereas the other chromosome has the allele f.

If the mother's genome is Ff, the F allele is transferred to some of the mother's egg cells, whereas the f allele is transfered to others. The resulting oocytes can be labelled as follows: F-egg and f-egg.

Similarly, if the paternal inheritance is Ff, the father's sperm cells can be either F-sperms or f-sperms.

If an f-sperm fertilizes an f-egg, the child will inherit the alleles ff. Because there is no F allele in the genome that causes freckles, the child does not develop freckles.


If a child has freckles, he or she has inherited an F allele from at least one of his or her parents.