In the age of genomics an accurate family history highlights diseases and conditions for which a particular person may be an increased risk. A person who learns that he or she may be vulnerable for a certain condition may seek early screening and periodic surveillance.
A person with significant coronary heart disease history (e.g., a cardiac event in a first-degree male relative <55 years or female relative <65 years) may be influenced to adopt a healthy lifestyle when possible to mitigate that risk.
The most fruitful way to complete family history is to send home a detailed questionnaire before the health care encounter because the information takes time to compile and often comes from multiple family members. Then you can use the health visit to complete the pedigree. A pedigree or genogram is a graphic family tree that uses symbols to depict the gender, relationship, and age of immediate blood relatives in at least three generations such as parents, grandparents, and siblings. Other relatives who are included in the genogram are aunts, uncles, nieces, nephews, and cousins. The health of close family members, such as spouse or partner and children, is equally important to highlight your prolonged contact with any communicable disease or environmental hazard such as tobacco smoke or to flag the effect of a family member’s illness on this person.
Record the medical condition of each relative and other significant health data such as age and cause of death, twinning, tobacco use, and heavy alcohol use. When reviewing your family history data, ask yourself specifically about coronary heart disease, high blood pressure, stroke, diabetes, obesity, blood disorders, breast/ovarian cancer, colon cancer, sickle cell anemia, arthritis, allergies, alcohol or drug addiction, mental illness, suicide, seizure disorder, kidney disease, and tuberculosis.
Your family tree is a good structure to place basic pedigree data such as this one which utilizes symbols depicting relationships. For each individual in your tree complete a form capturing physical traits and experiences.
This above diagram is a ledged or key to the family tree which is used in many disciplines.
Another consideration of the Family History record is recording your epigenetic state. Studies of suicide victims have suggested that people’s early experiences might influence the epigenic state of the DNA in their brains, and studies of monkeys have shown that their experiences influence the epigenic state of some of the DNA in their brains and blood. Because it is unethical to conduct certain kinds of experiments on human beings, we cannot prove that detrimental experiences early in life cause epigenic effects in people but armed with evidence that experiences affect epigenetic states in monkeys’ blood cells, we can at least look to see whether people’s epigenetic states are correlated with their experiences.
To date, several correlation studies of DNA extracted from human blood have been conducted, and because the data from these studies converge nicely with data collected in experimental studies of monkeys, a relatively clear picture is emerging regarding the effects of experiences on epigenetic marks.
Another family history document included here is a family tree diagraming your genetic genealogy which can also facilitate in further epigenetic studies. This genetic tree maps three genetic tests you can test for. One is the mitochondrial-DNA (mtDNA) which has an unique inheritance path from female to female. Males inherit their mother’s mtDNA, but cannot be passed down to their offspring.
In the below diagram, Joann has four offspring, one male and three female. All three of the females have offspring and pass their mtDNA, in the case of the male, her mtDNA stops with him. Joan’s descendants who have her mtDNA are shown in purple; notice great-grandchildren 3 and 4 have Joan’s mtDNA, but 1,2, and 5 don’t.
The second type of DNA test you could take is the Y-Chromosomal (Y-DNA) test. As you might guess, the Y-DNA chromosome is always passed down from the father to his son. Note that if a man has only daughters, his Y chromosome is not passed on to the next generation.
John’s descendants who have his Y-DNA are in blue; notice great-grand children 3 and 4 have John’s Y-DNA, but 1,2, and 5 don’t. Understanding these different DNA tests and their corresponding inheritance charts can help in genealogy research, but how about your epigenetic situation?
Unfortunately, it’s not that simple. In the above examples we’ve been talking about a single strand of chromosome, a specific strand of chromosome at that. Now consider that each chromosome is made primarily of a very long strand of DNA molecules, intertwined with itself in a heap, like a large skein of yarn unwound and packed up into a cohesive mass.
Now, a single DNA molecule is made of two very long chemical strands twisted around each other, like a thread that, when looked at closely, is seen to be made of two distinct strands of fiber wrapped around each other to form a single strand. Some stretches along the exceedingly long strand of DNA that makes up a chromosome do not have functions that we currently understand, but other segments are structured in such a way as to be helpful for cells when they produce molecules such as proteins. In epigenetics, its these protein segments that may activate or inactivate certain characteristics which may or may not impact our abilities and general health.
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