~50% for both? Has homosexuality been proven MORE genetically based than alcoholism?
I've wondered this with all the legislation being passed, vetoed, and/or discussed in the past few months.
One considered socially unacceptable.
One increasingly considered in the opposite fashion.
Both once labelled as diseases affecting loved ones or people we know.
Both sanctioned to various degrees by law and religion.
Both associated with increased risk of depression.
Both once considered matters of choice entirely.
Both now considered to have a genetic aspect separate from what many of us might consider "true" choice.
Most interestingly, though, the degree to which genetics seems to play a role in either case seems to be right around 50%.
Is such really the case?
If so, why?
Why do the numbers appear so similar to one another?
Why is one considered a matter of choice any more or less than the other?
What accounts for the differing perceptions?
Refer to the bolded and underlined sections for the 10 second summary.
Discuss.
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Twin studies of homosexuality have shown that identical twins are about twice as likely to both be gay compared to fraternal twins. This means that being gay is partly genetic and not simply something that a person learns or chooses to be.
There is one important thing to note, though. If the DNA sequence is the only thing determining whether someone is gay or not, we would expect that if one identical twin were gay, then the other would be too 100% of the time.
But this is not what scientists have found – the rate is actually closer to 50%. So while we know that genetics is involved, it doesn’t tell us the whole story. This is where environment comes in ...
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http://genetics.thetech.org/ask-a-geneticist/homosexuality
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GENETICS OF ALCOHOL USE DISORDER
How do genes influence alcoholism?
Alcoholism often seems to run in families, and we may hear about scientific studies of an “alcoholism gene.” Genetics certainly influence our likelihood of developing alcoholism, but the story isn’t so simple.
Research shows that genes are responsible for about half of the risk for alcoholism. Therefore, genes alone do not determine whether someone will become an alcoholic. Environmental factors, as well as gene and environment interactions account for the remainder of the risk.*
Multiple genes play a role in a person’s risk for developing alcoholism. There are genes that increase a person’s risk, as well as those that may decrease that risk, directly or indirectly. For instance, some people of Asian descent carry a gene variant that alters their rate of alcohol metabolism, causing them to have symptoms like flushing, nausea, and rapid heartbeat when they drink. Many people who experience these effects avoid alcohol, which helps protect them from developing alcoholism.**
As we have learned more about the role genes play in our health, researchers have discovered that different factors can alter the expression of our genes. This field is called epigenetics. Scientists are learning more and more about how epigenetics can affect our risk for developing alcoholism.
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http://www.niaaa.nih.gov/alcohol-health/overview-alcohol-consumption/alcohol-use-disorders/genetics-alcohol-use-disorders
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Twin Studies and Adoption Studies: Is Alcoholism Inherited
“Relatives of alcoholics have higher rates of the disease than do relatives of non-alcoholics. But is this nature or nurture? Perhaps some of each, but let’s look at the evidence for heredity.
“Twin studies offer a chance to compare the influence of genetics versus environment. Identical twins (one-egg twins) share exactly the same set of genes while fraternal twins (two-egg twins), like ordinary siblings, share only one-half their genes. A higher rate of concordance (similarity) between identical twins compared with fraternal twins would argue for heredity. In other words, how often are both twins affected together rather than only one. The evidence favors heredity with figures like 60% (identical) versus 39% (fraternal) in one Scandinavian study.
“Even more interesting are the results from adoption studies. When adopted in infancy and studied into adulthood, sons of alcoholics were 4 times as likely to be alcoholic as were sons of non-alcoholics. And this risk was not affected by the alcoholism status of the adopted parent!
“Certainly heredity cannot account for all causation in alcoholism but in that manner it is much like diabetes or heart disease that also have an inherited component.”
From ASK DR. BOB, published by NCADD and written by Robert M. Morse, MD, former Director of Addictive Disorders Services at the Mayo Clinic, NCADD Board Member and member of NCADD’s Medical/Scientific Committee.
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https://ncadd.org/for-parents-overview/family-history-and-genetics/226-family-history-and-genetics