It showed that there was clearly more to inheritance than simply the coded sequence of DNA.
We then realized that we were dealing with what is now known as genomic imprinting. What genomic imprinting means is, in a nutshell, that genes have a memory of where they came from.
Something other than just the DNA was capable of moving between generations. It was a tantalizing glimpse into this unknown and unexpected world. A hidden layer acting on and able to directly control how our genes function. It meant that inheritance was not simply about which genes you inherited, but whether those genes were silenced, switched on or off.
And you can think of it as a, as a light switch. Switch on the gene, the light is shining, the gene is active, makes, makes a cell do a certain thing. Or the light switch is off, everything is dark, that gene is off. The switches remain on or remain off, and that gives the cells their identity.
The activity of genes was being controlled by a switch--the attachment of a simple chemical which dictated whether the gene was switched on or off.
Whether those genes are turned on or off is called epigenetics.
Epigenetics, er, you know, up on the genes.
Not only is the sequence important for the DNA, which we've studied for a long time in the past few decades, but we now understand that in addition to that there is this overlying epigenetic phenomenon that allows the genes to get turned on or off.
Epigenetics could explain how a human could be created with less than 30,000 genes and why the Genome Project didn't provide all the answers.
Now if we actually put epigenetics on top of it, where makes it much more complicated on whether genes get activated and to a certain level and so forth. Then you have a complexity that can start to explain biology much more effectively than the simple sequence of the DNA.
So clearly we have additional levels of complexity that we now need to understand that are beyond the DNA.
The next huge challenge for modern biology is to now decipher the epigenetic code and understand all the combinations of switches that exist.
An accurate chemical map of the human genome tells us surprisingly little about how it actually works. Transcribing the code of the genes, the Genome Project is not an end, but simply a beginning.
words to memorize
1. genomic imprinting:基因記憶
genomic correlation 基因相關(guān)
genomic exclusion 基因排斥
2.in a nutshell:簡(jiǎn)單說(shuō)來(lái)
3.epigenetics:實(shí)驗(yàn)胚胎學(xué)
epigenetic:后天生成的，外遺傳的
