Short Answer 
The earlobe shape is determined by a dominant (F) for detached earlobes and a recessive (f) for attached earlobes. Blood type inheritance involves alleles A, B (dominant) and O (recessive), while Joseph, who has a blood type of BO and Rh factor positive, indicates he carries a recessive O allele inherited from his family, which matches the genetic profile from his partner Rita.
Step 1: Understand Earlobe Inheritance
The shape of the earlobe is controlled by a single autosomal gene with two alleles: dominant (F) for detached earlobes and recessive (f) for attached earlobes. Depending on the allele combinations inherited from parents, different patterns of earlobe shapes can occur. For example:
- If both parents are FF, all offspring will have FF and present free earlobes.
- If one parent is Ff and the other is ff, there will be a 50% chance for free earlobes and a 50% chance for attached earlobes.
Step 2: Explore Blood Type Inheritance
Blood type inheritance is based on three alleles: A, B, and O. Here, both A and B are dominant while O is recessive. Blood types can be classified as A (AA or AO), B (BB or BO), AB (both A and B), or O (OO). Additionally, the Rh factor is independently inherited and can be Rh+ or Rh- based on the presence or absence of the RHD gene.
- Type A: Alleles AA or AO
- Type B: Alleles BB or BO
- Type AB: Alleles AB
- Type O: Alleles OO
Step 3: Analyze Joseph’s Blood Type
Joseph has a blood Rh factor of + and is determined to have a blood type of BO. This conclusion comes from analyzing the inheritance of blood types in his family. Even though his partner, Rita, is type AB, one of their daughters, type A, married a type B and had a son with type O blood, indicating that Joseph must carry a recessive O allele that Rita masked with her dominant alleles.
- Joseph’s ability to pass the O allele comes from having a BO genotype.
- Rita’s AB type means she carries no O allele, thus confirming Joseph’s inheritance pattern.