A lady visited a genotype testing center with her boyfriend for routine screening. After the test, her result showed that she had the AS genotype. This outcome surprised her because she had always known that both her parents were genotype AA. Concerned about the discrepancy, she raised the issue in the presence of her father. During the discussion, her father expressed doubt, suggesting that he might not be her biological parent. To clarify the situation, they both agreed to undergo a DNA test at the hospital. The DNA test results later confirmed that her father is indeed her biological parent. This situation raises an important question: how can the lady have an AS genotype when both of her parents are believed to have AA genotypes? @all

Welcome back — missed you this week. Let's solve this genetic puzzle. Step 1: Understand the genotypes A genotype* describes the genetic makeup of an individual. In this case, we're looking at the alleles for hemoglobin. An individual with genotype AA is homozygous* for the A allele, meaning they have two A alleles. They can only pass on an A allele to their offspring. An individual with genotype AS is heterozygous*, meaning they have one A allele and one S allele. They can pass on either an A allele or an S allele to their offspring. Step 2: Expected inheritance from two AA parents If both parents have the AA genotype, they can only contribute an A allele to their child. Parent 1 (AA) → contributes A Parent 2 (AA) → contributes A Therefore, any child born to two AA parents must have an AA genotype*. Step 3: The discrepancy The lady has an AS genotype. This means she received an A allele from one parent and an S allele from the other parent. The problem states that her father is confirmed biological and has an AA genotype. This means he contributed an A allele to her. For the lady to have an AS genotype, she must have received an S allele from her mother. Step 4: Conclusion Based on the principles of genetic inheritance, if the lady has an AS genotype and her biological father is AA, then her mother cannot have an AA genotype. The mother must carry the S allele to have passed it on to her daughter. Therefore, the mother's genotype must be AS (or SS, though AS is more common for carriers). The lady's long-held belief that both her parents were AA was incorrect regarding her mother's genotype. What's next?