Genetic inheritance Questions

  1. Which of the following applies to the condition in this family?

The condition in the family is caused by variable expressivity. Variable expressivity refers to when a phenotype is expressed in different degrees among people who have a similar genotype.  In the Winslow family both parents have mild heartbeat irregularity, but they do not show symptoms. The inherited genes that cause heartbeat irregularity are more expressed in Shiloh and his younger brother Pax. They had the full syndrome due to the degree of the expressivity of the genes that cause heartbeat irregularity. However, Vivienne who is still a baby did not inherit these genes from the parents and hence he had a normal heartbeat.

  1. How is the inheritance pattern of this form of long QT syndrome similar to that of familial hypercholesterolemia?

The inheritance patterns of Long QT genetic disorder and familiar hypercholesterolemia are similar in that they are both caused by autosomal dominant genes (Kimura, 2008).These disorders can be inherited through acquiring an abnormal gene from an individual’s parents who carry the genes that cause the disorders. A parent who carries the disease causing-mutation of these two disorders has a 50% chance of transmitting the disorders to their child. There are other cases where a child can inherit the genes that cause the disorders from both parents.

  1. How is it possible that Vivienne did not inherit either the serious or asymptomatic form of the illness?

It is possible for Vivienne not to have inherited either the serious or the asymptomatic form of the illness because she inherited the recessive gene that causes the disorder from the parents. She did not inherit the dominant gene that causes the disorder and hence she does not have the genes that cause the disorder.

  1. Do the treatments for the condition affect the genotype or the phenotype?

The treatments for the Long QT syndrome affect the individual’s genotype. The therapy used to treat the syndrome is genotype guided that allows an effective individually tailored therapy (Kimura, 2008).

  1. What is the chance that, if they have a child, he or she will have a porphyria?

Congenital erythropoietic porphyria and ALA dehydratase deficiency are both rare autosomal recessive disorders.  If Barnabas and his wife Angelique get a child, there is a 505 chance of the child having porphyria. The father is a carrier of the genes for the disorder, and he is already suffering from the disorder. It means that there is a 50% chance of their child inheriting the genes causing the disorder from the father.

Kimura, R. (2008). Genetic inheritance patterns. New York: Nova Biomedical Books.