Common Misconceptions

Misconception: "Carriers of cystic fibrosis are ill or show some symptoms."

Reality: Carriers (Ff) are completely unaffected. They have one working copy of the dominant allele, which produces enough functional CFTR protein for normal health. The carrier has no way of knowing they carry the allele without a genetic test — which is why two apparently healthy parents can unexpectedly have a child with CF.

Misconception: "Two healthy parents cannot have a child with cystic fibrosis."

Reality: If both parents are carriers (Ff), they are healthy but each carry one recessive allele. A Punnett square for Ff x Ff gives a 1 in 4 (25%) probability of an ff child, who will have CF. This is exactly how most CF cases arise — neither parent has the condition, but both carry the allele.

Misconception: "Polydactyly must skip generations because it is genetic."

Reality: Polydactyly is caused by a dominant allele, so it cannot skip generations — if the allele is present, the condition is expressed. However, individuals with polydactyly (Pp) have a 50% chance of not passing it to each child. It is also possible for a new mutation to occur, causing polydactyly in a child with unaffected parents, but this is uncommon.

Misconception: "Genetic testing for embryos is compulsory when parents are carriers."

Reality: Genetic testing is always a personal choice. Pre-implantation genetic diagnosis is available to couples who are known carriers, but it is not compulsory. There are significant ethical debates about who should be tested, who should have access to the results, and whether selecting embryos based on genetic criteria is morally acceptable.