This is another critical subject area of core medical definitions and again there are contradictions, ambiguity, and imprecision widely in use.
Be aware that none of the core medical definitions here lose their precision and consistency if you prefer to draw the line at birth rather than at conception?
Like with the Google results linked above, earlier my own definition too said: "passed on with the DNA". Then the newest research results in the realm of Epigenetics made me realize that such notion is superfluous and makes inherited traits definitions needlessly contradictory.
Because "epi" is Greek and can have several meanings: "near", "above", "before", "after",... - giving Epigenetics the semantic meaning of "in addition to changes in genetic sequence".
This is because Epigenetics is the study of heritable changes in gene expression (ie which genes are active vs which genes are inactive) that do not involve changes in the underlying DNA sequence (a mutation).
In other words, Epigenetics is the study of heritable changes in phenotype without underlying changes in genotype.
A change in characteristics without a change in genome.
And so, if epi traits can be inherited in addition to genetic traits then we must not restrict inherited traits to those passed on with the DNA. You see that?
And either way there is no need for such restriction, see below.
What I always miss in Epigenetics studies is the consideration of triggers. Because in many or all(?) studied cases it may be the triggers that lead to gene expression and shape the phenotype after conception.
Regardless whether that's the case, this shows yet again the necessity to understand cause vs symptom vs trigger, so as to more completely study all three.
Either way, you see there is no need to stuff the definition of inherited traits with the notion how they get inherited:
The fact that we clarified here "passed on at conception" is sufficient to obtain the clear, precise, and consistent medical definitions.
Inherited Traits vs Heritable Traits
Contrary to earlier accepted knowledge, the newest research results in the realm of Epigenetics suggest that certain acquired characteristics can be inherited by offspring. For your interest I have included a few links in the footnotes.
Note that again there is no need to stuff the definition of acquired traits with the notion whether or not they can be passed on to offspring.
(This is what Epigenetics looks at: identifying traits that can be passed on to offspring although they are not coded in the DNA)
The fact that we clarified "gained after conception" is sufficient to obtain the clear, precise, and consistent medical definitions.
Inherited vs Acquired: Clarification
Let's bring more clarity to the terminology mess out there!
At this point you may be wondering "Where are the contradictions, ambiguity, and imprecision relating to Inherited Traits vs Acquired Traits?"
I decided to "outsource" them to standalone chapters for the same reason why I introduced the word "traits" in this chapter: There is significant search volume only for:
Inherited Traits Examples
- A homozygous SOD1 A mutation causes inherited Degenerative Myelopathy (DM, a defect) in every dog, and inherited Amyotrophic Lateral Sclerosis (ALS, or Lou Gehrig's defect) in every person.
- A different mutation causes a deficiency in the blood clotting factor vWF (von Willebrand Factor) in every patient, therefore leading to the inherited von Willebrand defect
When a newborn baby or puppy carries a defect this by itself does not mean that the defect is inherited: Many defects (and indeed disorders and diseases too) are acquired prenatal in the uterus or through the umbilical cord.
Acquired Traits Examples
- An injury to the ear drum from close gun shots causes an acquired hearing defect in every patient (dog or person).
- Radiation assumed during one's lifetime or in a short period of time may cause or trigger an acquired immune system disorder.
- Any of the six key mistakes commonly made with vaccinations may cause or trigger an acquired bacterial infection (a disease) - because every vaccination overall weakens the immune system, and so all body systems!
The Argument: "Runs in Families"
Great examples, and all relevant for both people and dogs:
Unless the cause of a condition is a (known or yet unknown) mutation existing in the genetic code of one or both direct ancestors, the discovery "it runs in families" may mean that the family's behavior is adopted rather than a defect inherited.
Pronounced living characteristics are sometimes (consciously or subconsciously) adopted by children, grandchildren, and so forth. Only pronounced living characteristics can lead to a disorder, and disorders cannot be inherited.
Alternatively it may mean that the affected descendants are affected by the same (or another) pathogen or chemical substance (in medication, "food", household, or environment) that causes the observed condition.
If an ailment other than a disease shows only later in life, and outside the biological transitions, it almost certainly is not an inherited defect but an acquired disorder or an acquired defect (in this order).
Inherited defects exist at conception, and so they either show right from birth or they start to show with biological transitions.
Biological transitions are the obvious puberty, pregnancy, and menopause, as well as less obvious transitions like teething, end of hypertrophy (increase in cell size), end of hyperplasia (increase in rate of cell division), atrophy (wasting away of an organ or other tissue structure), and others.
Footnotes: See for example as per your preference:
- Extracellular vesicles as emerging intercellular communicasomes
- Memories Can Be Inherited, and Scientists May Have Just Figured out How
- Epigenetic inheritance of acquired traits through sperm RNAs and sperm RNA modifications: "Once deemed heretical, emerging evidence now supports the notion that the inheritance of acquired characteristics can occur through ancestral exposures or experiences and that certain paternally acquired traits can be 'memorized' in the sperm as epigenetic information."
- How Dad’s Stresses Get Passed Along to Offspring
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