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?

Is nail–patella syndrome a dominant or a recessive condition? Explain your reasoning.

Verified step by step guidance

1. Step 1: Understand the inheritance patterns of dominant and recessive traits. A dominant trait requires only one copy of the allele to be expressed, while a recessive trait requires two copies of the allele to manifest in an individual.
2. Step 2: Examine the pedigree provided in the problem. Look for patterns of inheritance across generations. Specifically, check if the condition appears in every generation (indicative of dominance) or skips generations (indicative of recessiveness).
3. Step 3: Identify whether affected individuals have at least one affected parent. If affected individuals consistently have at least one affected parent, this supports the condition being dominant.
4. Step 4: Analyze unaffected individuals in the pedigree. If unaffected individuals do not pass the condition to their offspring, this further supports dominance, as recessive conditions can be carried silently by heterozygous individuals.
5. Step 5: Consider additional evidence, such as the co-occurrence of nail–patella syndrome with ABO blood type, to ensure the inheritance pattern aligns with the dominant trait hypothesis. Use this reasoning to conclude whether the condition is dominant or recessive.

Key Concepts

Autosomal Dominance and Recessiveness

Autosomal dominance and recessiveness refer to how traits are inherited through genes located on non-sex chromosomes. In dominant conditions, only one copy of the mutated gene is needed for the trait to manifest, while in recessive conditions, two copies are required. Understanding these inheritance patterns is crucial for analyzing genetic disorders like nail–patella syndrome.

Pedigree Analysis

Pedigree analysis is a method used to trace the inheritance of traits through generations in a family. By examining the pedigree, one can determine how a genetic condition is passed down, identifying affected individuals and their relationships. This analysis helps in deducing whether a condition is dominant or recessive based on the presence or absence of the trait in family members.

ABO Blood Type Inheritance

The ABO blood type system is an example of codominance and multiple alleles, where individuals can inherit one of four blood types (A, B, AB, or O) based on the alleles they receive from their parents. Understanding this system can provide insights into genetic inheritance patterns and help differentiate between traits that are inherited independently versus those that may be linked to other genetic conditions, such as nail–patella syndrome.