My man's got a bad case of cystic fibrosis A hella pessimistic prognosis He started out like "why god, why god? Why did that song have to shuffle on my iPod?" Feelin' like he got struck with a left He did the sensible thing and read a textbook And discovered an inherited disease That can only be understood evolutionarily He's got a gene called CFTR With one deletion in a phenylalanine part One less amino acid, Fantastic Hell-a-common, One in thirty white people have it Carry one copy and you don't even notice Inherit two copies and catch a diagnosis An autosomal recessive disorder, One of more than Four thousand genetic diseases recorded And my man got the shorter side of the stick So he started askin' questions like "why does it exist?" What kind of sadistic joke is cystic fibrosis? Now this is what he sings when he's feelin' hopeless I live my life, I love my friends, I eat my food Sometimes I just don't understand the things I do A wise man told me: "Look deeper inside you" So now I take the gene's eye view It turns out my man's got a special mutation That goes back more than six hundred generations CFTR is just one of twenty thousand Protein-coding genes that have been accounted Knock one out and it makes a vast difference He can't breathe right, And he's got no vas deferens That's infertility without medical help So how did this gene spread itself so well That one in every thirty caucasian people have it? He found the answer: Heterozygote advantage Two copies gives you cystic fibrosis One copy protects you from tuberculosis Mendelian diseases can spread because carriers Get resistance to parasites like various Malarias, just check out thalassemia It's common in the tropics like sickle cell anemia My man's mutation protected his ancestors In times of pandemic it spread and became prevalent So evolution sacrificed him for his relatives And now this is what he sings when he's feelin' sick I live my life, I love my friends, I eat my food Sometimes I just don't understand the things I do A wise man told me: "Look deeper inside you" So now I take the gene's eye view My man studied evolution up to his eyeballs Until at least he could say "Hey, this isn't my fault" It's all about trade offs and average benefits Across populations; Sometimes it's genetic drift Or founder effects, It's not always adaptive Sometimes mutations just randomly happen Sex chromosomally x-linked recessives Only affect men and yeah, That's kinda sexist Some are autosomal dominant like Huntington's Which only kicks in after reproduction's done So selection can't eliminate it Maybe human ingenuity can though; It's innovative Some disorders are so rare they're orphaned And never get a piece of the research portion My man's only one in three thousand But in 2015 you can be one in three hundred thousand And still be counted by patient advocates Genetic research is takin' massive steps My man's gettin' hitched and family planning With his new gene's eye view understanding I live my life, I love my friends, I eat my food Sometimes I just don't understand the things I do A wise man told me: "Look deeper inside you" So now I take the gene's eye view I live my life, I love my friends, I eat my food Sometimes I just don't understand the things I do A wise man told me: "look deeper inside you" So now I take the gene's eye view