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.

Does this family give evidence of genetic linkage between nail–patella syndrome and ABO blood group? Why or why not?

Verified step by step guidance

1. Step 1: Understand the concept of genetic linkage. Genetic linkage occurs when two genes are located close to each other on the same chromosome, causing them to be inherited together more often than expected by chance. In this case, we are investigating whether the gene responsible for nail–patella syndrome is linked to the gene determining ABO blood type.
2. Step 2: Examine the pedigree provided. Identify individuals affected by nail–patella syndrome and their corresponding ABO blood types. Look for patterns in inheritance that suggest these traits are inherited together.
3. Step 3: Determine the expected inheritance patterns if the traits are unlinked. For unlinked traits, the inheritance of nail–patella syndrome and ABO blood type should occur independently, following Mendelian principles.
4. Step 4: Compare the observed inheritance patterns in the pedigree to the expected patterns for unlinked traits. If the traits are linked, you would expect certain combinations of nail–patella syndrome and ABO blood type to appear more frequently than others.
5. Step 5: Evaluate whether the data from the pedigree provides statistical evidence of linkage. This can be done using a chi-square test or by calculating recombination frequencies. If the recombination frequency is significantly less than 50%, it suggests linkage between the two traits.

Key Concepts

Genetic Linkage

Genetic linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together during meiosis. When two traits are genetically linked, they do not assort independently, which can be observed in pedigree analysis. If the inheritance patterns of two traits, such as nail–patella syndrome and ABO blood type, show a consistent correlation, it suggests they may be linked.

Pedigree Analysis

Pedigree analysis is a diagrammatic method used to trace the inheritance of traits through generations in a family. It helps in identifying patterns of inheritance, such as autosomal dominant or recessive traits. By examining the pedigree for nail–patella syndrome and ABO blood type, one can determine if the traits are inherited together, which is crucial for assessing genetic linkage.

Autosomal Inheritance

Autosomal inheritance refers to the transmission of genes located on the autosomes, which are the non-sex chromosomes. Nail–patella syndrome is an autosomal disorder, meaning it can affect both males and females equally and follows Mendelian inheritance patterns. Understanding whether the traits in question are autosomal helps clarify the expected inheritance patterns and their potential linkage.