Looks like mom and dad are to blame for all those ups and downs headed your way in marriage—and if you think that size does matter in a relationship, you are correct.
A new study by UC Berkley and Northwestern University found that people who have a certain gene variant known as the HTTLPR allele tend to be either super happy or super miserable in their relationship, and it all has to do with the size of that allele. People who inherited one or two long 5-HTTLPR alleles from each parent were less likely to be negatively affected by different emotional changes in their relationship, while those with two short alleles were more prone to becoming very upset when experiencing tension in their relationship—and elated when things were going well.
But don't throw up your hands and declare that you've got no control over your roller coaster of emotions just yet—and furthermore, this all doesn't mean that two people with all kinds of different alleles can't be compatible. Claudia M. Haase, assistant professor of human development and social policy at Northwestern University, says "Neither of these genetic variants is inherently good or bad. Each has its advantages and disadvantages." So, see? It's all about taking the good with the bad, just like marriage.
For more info on just how researchers went about conducting this study, go here.