Nail–patella syndrome is an autosomal disorder affecting the shape of nails on fingers and toes as well as the structure of kneecaps. The pedigree below shows the transmission of nail–patella syndrome in a family along with ABO blood type. Is nail–patella syndrome a dominant or a recessive condition? Explain your reasoning.

Verified step by step guidance

1. <Step 1: Understand the genetic basis of the disorder. Nail–patella syndrome is an autosomal disorder, meaning the gene responsible is located on one of the non-sex chromosomes.>
2. <Step 2: Analyze the pedigree. Look for patterns in the inheritance of the disorder across generations.>
3. <Step 3: Identify if the disorder appears in every generation. If it does, this suggests a dominant pattern. If it skips generations, it may be recessive.>
4. <Step 4: Check if affected individuals have at least one affected parent. In a dominant disorder, affected individuals typically have an affected parent.>
5. <Step 5: Consider the possibility of new mutations or incomplete penetrance, which can sometimes complicate the analysis of pedigrees.>

Key Concepts

Autosomal Dominance and Recessiveness

Autosomal dominance refers to a pattern of inheritance where only one copy of a mutated gene from an affected parent can cause the disorder. In contrast, autosomal recessiveness requires two copies of the mutated gene for the condition to manifest. Understanding these patterns is crucial for analyzing pedigree charts and determining the inheritance of traits.

Pedigree Analysis

A pedigree chart is a visual representation of a family's genetic history, showing how traits are passed through generations. By examining the presence or absence of a condition in family members, one can infer whether a trait is dominant or recessive. This analysis helps identify carriers and predict the likelihood of the condition appearing in future generations.

ABO Blood Type Genetics

The ABO blood type system is determined by the presence of specific antigens on the surface of red blood cells, which are inherited in a codominant manner. Understanding blood type inheritance can provide additional context in pedigree analysis, as it may help differentiate between individuals with similar phenotypes and clarify the genetic relationships within the family.