This toolkit is based on the Global Genes Webinar How to Discuss Genetic Disease with Your Loved Ones that was originally webcast April 1, 2015. A replay can be viewed at http://globalgenes.org/april2015webinar/.
There are currently about 7,000 rare diseases identified worldwide, and approximately 80 percent of these are caused by genetic changes. This toolkit will provide some basics on genetic diseases, how and when patients might want to discuss details of their disease with others, and with whom.
Each person has their own genome, a genetic blueprint consisting of deoxyribonucleic acid, or DNA. DNA is a molecule that is shaped like a twisted ladder and is contained in virtually all of the cells of the body. Each person’s DNA contains a unique set of instructions that determines the characteristics of an individual.
Within a person’s cells, DNA is coiled up and stored within 23 pairs of chromosomes with one set of 23 coming from the father and the other set of 23 coming from the mother. Within the chromosomes, tiny segments of DNA form genes. Depending on the type of cell, certain genes will be activated to perform specific functions.
Genes make proteins, which carry out various functions within the body. In the case of a genetic disease, a mutation in the gene may prevent a needed protein from being made or carry out some other interference to the proper functioning within the body. People have two copies of each gene in their body with one derived from their mother and one derived from their father.
One Way to Distinguish Genetic Diseases
One difference in the various genetic diseases is how they are passed on between parent and child. Some genetic diseases may require that just one parent pass on the mutation in a gene (autosomal dominant). Other diseases require mutations from both parents for them to manifest (autosomal recessive). In some cases, someone may carry a genetic disease, but show no signs for having the disease themselves. Still, in other cases, a person with a genetic disease may have a mutation that is not present in either the mother of father (de novo).
Autosomal Dominant: If one parent carries a mutation for an autosomal dominant genetic disease, the couple’s child has a one in two (50 percent) chance of having that genetic disease.
Autosomal Recessive: If both partners carry mutations for an autosomal recessive genetic disease, their child has a one in four (25 percent) chance of having that genetic disease.
X-Linked Recessive: X-linked genetic diseases are passed on by the X chromosome that determines the sex of a person. Males have a Y chromosome from their father and an X chromosome from their mother. Females have an X chromosome from than father and a second X chromosome from their mother. If the female partner is a carrier of an X-linked genetic disease, her male child has a one in two (50 percent) chance of having that genetic disease. Because females have two X chromosomes, whereas males only have one, these diseases tend to show up predominantly in males or are generally more severe in males.
De Novo Mutations: Some genetic mutations are not passed on from a person’s parent, but begin with the individual. These types of genetic mutations are referred to as “de novo.”