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.

Using N and n to represent alleles at the nail–patella locus and Iᴬ, Iᴮ and i to represent ABO alleles, write the genotypes of I-1 and I-2 as well as their five children in generation II.

Verified step by step guidance

1. Step 1: Understand the inheritance pattern of nail–patella syndrome. It is an autosomal dominant disorder, meaning that individuals with at least one dominant allele (N) will express the syndrome. The recessive allele (n) does not cause the syndrome.
2. Step 2: Review the inheritance pattern of ABO blood types. ABO blood type is determined by codominant alleles Iᴬ and Iᴮ, and the recessive allele i. Individuals with IᴬIᴬ or Iᴬi have type A blood, IᴮIᴮ or Iᴮi have type B blood, IᴬIᴮ have type AB blood, and ii have type O blood.
3. Step 3: Analyze the pedigree provided. Determine the phenotypes of I-1 and I-2 (the parents) for both nail–patella syndrome and ABO blood type. Use this information to deduce their genotypes. For example, if I-1 has nail–patella syndrome, they must have at least one N allele.
4. Step 4: Examine the phenotypes of the five children in generation II for both nail–patella syndrome and ABO blood type. Use the rules of inheritance to deduce their genotypes based on the parents' genotypes and the observed traits.
5. Step 5: Write the genotypes for I-1, I-2, and each of the five children in generation II. Ensure that the genotypes include both the nail–patella alleles (N and n) and the ABO alleles (Iᴬ, Iᴮ, i).

Key Concepts

Autosomal Inheritance

Autosomal inheritance refers to the transmission of genetic traits that are located on the autosomes, which are the non-sex chromosomes. In the case of nail-patella syndrome, it is inherited in an autosomal dominant manner, meaning that only one copy of the mutated allele (N) is sufficient to express the disorder. Understanding this concept is crucial for determining the genotypes of affected individuals in a pedigree.

Pedigree Analysis

Pedigree analysis is a method used to trace the inheritance patterns of traits through generations in a family. It visually represents relationships and can indicate whether a trait is dominant or recessive. By analyzing the pedigree provided, one can deduce the genotypes of individuals based on their phenotypes and the inheritance patterns observed.

Blood Type Genetics

Blood type genetics involves the inheritance of ABO blood group alleles, which include Iᴬ, Iᴮ, and i. The combination of these alleles determines an individual's blood type (A, B, AB, or O). Understanding how these alleles interact, particularly in conjunction with other genetic traits like nail-patella syndrome, is essential for accurately determining the genotypes of the individuals in the pedigree.