Question

What is the example of the inheritance pattern shown?

A. Phenylketonuria
B. Sickle cell anemia
C. Haemophilia
D. Thalassemia

Answer 1

To understand patterns of disease transmission, the basic laws of inheritance are essential. For single-gene disorders, there are five specific inheritance modes: autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, and mitochondrial.

Complete answer: Phenylketonuria- In an autosomal recessive pattern, PKU is hereditary in families. Autosomal recessive inheritance means that the gene that is altered has two copies of an individual. Each parent of a person who has PKU typically carries one copy of the altered gene.
Sickle cell anemia- Sickle cell anemia is an autosomal recessive disorder, which means that it only happens if both the maternal and paternal copies of the HBB gene are defective. In other words, if a person receives only one copy of the defective HBB gene, they do not have sickle cell anemia, but have what is called a sickle cell trait, either from their mother or their father. There are typically no signs of complications for people with sickle cell traits, but they can pass on the mutated gene to their children.
Hemophilia- In an X-linked recessive pattern, hemophilia A and hemophilia B are inherited. On the X chromosome, which is one of the two sex chromosomes, the genes associated with these conditions are found. One altered copy of the gene in each cell is necessary for males (who have only one X chromosome) to induce the disorder.
Thalassemia- Thalassemia is usually inherited in an autosomal recessive manner; however, the inheritance can be very complex as hemoglobin development can be affected by multiple genes. In both copies of the HBB gene in each cell, most individuals affected by beta-thalassemia have mutations.

Hence the correct answer is option C, Hemophilia.

Note: An X-linked recessive condition is hemophilia. On the X chromosome, the genes associated with this condition are located and are inherited in a cross-cutting manner. This suggests that this disease is transmitted to their sons by the mothers and the fathers pass the illness to the daughters.