Question

Mr. Wayne is a 38-year-old man with a significant family history of elevated cholesterol levels. His father died at age 42 from a massive heart attack secondary to elevated cholesterol and triglycerides, and two of his older siblings are currently taking medications to lower their cholesterol levels. Mr. Wayne makes an appointment to discuss his risk for hypercholesterolemia. The nurse recognizes that Mr. Wayne is at risk for familial hypercholesterolemia because this is an autosomal dominant inherited condition. (Learning Objective 2)

Describe the pattern of autosomal dominant inheritance.

Mr. Wayne asks what chance his children have of developing familial hypercholesterolemia. How should the nurse respond?

Explain the phenomenon of penetrance observed in autosomal dominant inheritance.

Answer 1

The genes located on the chromosomes in our cells, provide the genetic information about growth, development and function of our bodies. A change in this genetic information causes genes not to work properly which is called mutation. The pattern of inheritence of this mutated gene depends on:

• whether mutated gene is located on the chromosome numbered 1-22 called autosomal
• If the mutated gene is located on sex chromosome
• variation of genetic information that makes a gene mutated is recessive or dominant.

Based on inheritence of genetic condition due to change in single gene is categorized as:

1. Autosomal dominant
2. Autosomal recessive
3. X-linked dominant
4. X-linked recessive

These inheritence pattern explains how the disease is transmitted in families. It also helps to predict the chances of reoccurence of risk for relatives.

The Autosomal dominant inheritence can be explained as:

• The Autosomal dominant inheritence is also called as vertical inheritence beacuse of transmission from parent to offspring.
• In the autosomal dominant inheritence a single mutated gene is present.
• In every pregnacy there is 50 % of chances for the offsprings to develop the disease.

ANSWER 2) Mr Wayne is at risk of developing hypercholesterolemia due to the autosomal dominant inherited condition that results in vertical transmission of disease. But Mr.Wayne has not yet developed the disease so the chances of his children receiving the disease is nill. But if he acts as a carrier with single mutated gene present then his children will have 50 % chance of developing or not developing the disease.

ANSWER 3) Penetrance in genetics is the proprtion of individual carrying a particular mutated gene and its associated trait. In autosomal dominant inheritence, a condition is said to show penetrance if clinical symptoms are present in the individuals who have the disease causing mutation. This is called complete penetrance. If the individual have the disease causing mutation i.e the mutated gene but do not show the associated trait or clinical symptoms then its said to be incomplete penetrance. Some of the dominant genes in some cases have reduced penetrance. It means the individual may have a dominant gene but may not show the signs of the genes. The penetrance is affected by environmental factors,age, lifestyle and other genetic factor. For example: a person may posses the mutated gene for cancer but its not necessary that they will immediately develop cancer.