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Current time:0:00Total duration:4:29
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Video transcript

so the past videos of this series have been a pretty continuous discussion about our genes so our genes and our environment related to our behavior and to say that the genes and the environment are both important is really true but but really more specifically they interact and so I've alluded to this previously with the tea and the hot water example but I'm going to get really specific with the language here because not only do our genes and our environment both affect our behavior their effect is really dependent on each other ok so say you have two babies in the nursery of a hospital one will say is genetically predisposed to be much more attractive than the other one so we have this attractive baby and we have this really this really hideous baby and as a result the beautiful baby over here it receives more affection more attention and it grows up to to be generally more sociable and well-adjusted but suppose even further that at birth both of these babies share a combination of genes that predisposes depression as we've learned the environment activates those genes so in this case maybe the genes are activated by environmental stressors so both babies have these genes but throughout life this cute and ultra lovable baby is surrounded by this great and supportive Network and it has reduced stress so it's its genes aren't stimulated to create the combination of neurotransmitters and and other proteins that are involved in depression but over here this ugly baby is cranking out these proteins like crazy and maybe that's because this baby is getting made fun of all the time or or maybe it's because it just it has less friends so I guess the cute baby's genes are somewhat responsible for setting up the environment but really also the environment is responsible at least to some degree in keeping those depression genes at bay similarly the less fortunate baby over here his genes play a role in his tough life and and that tough life is activating the genes that are associated with creating the neurotransmitters of depression so this is kind of a crude example of gene and environment interacting with each other but a more specific example is the genetic condition PKU or phenylketonuria so p k you and phenylketonuria is a genetic condition in humans that's caused by mutations to a gene that code for a liver enzyme and that liver enzyme is phenylalanine hydroxylase so so PAH but because the enzyme is missing the amino acid phenylalanine it doesn't get converted into the amino acid tyrosine during one of the metabolic pathways in our body and so this this causes a buildup of phenylalanine in the body which can cause problems for brain development and and even other problems so PKU it affects one in about 15,000 babies in the US but most of these babies grow up without any major problems and it turns out that during infant screening these babies are identified in their place on a special phenyl alanine free diet so because they're not taking in all of this phenyl alanine it's it's resulting in a less problematic buildup of the phenylalanine in the body so it's really an interaction again between our genes and our environment that initiates the body's responses and behavior so we see that the environment is dependent on a genetic predisposition but gene expression is also dependent on the environment and this is the phenomenon that we're referring to as gene environment interaction so this idea is going to shift our vocabulary away from phrases like nature versus nurture and it's going to bring us to a more correct phraseology nature through nurture
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