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Introduction to Pedigrees

Author(s): Lisa M. Meffert, PhD

Marfan's Syndrome: Parent–offspring Relationships

Now we will begin to consider parent-offspring relationships. At first glance, we do not know if individual #1 is heterozygous or homozygous for the "M" allele. However, note that when she mates with a normal male, she produces some normal offspring. Thus, we can conclude that she is a heterozygote. If she were homozygous for "M," then every one of her offspring would receive the allele for Marfan's syndrome. The same logic applies to assigning the genotype to individual #2.