The article, an excerpt from the chapter "The First Derivative of Identity" of his book The Gene: An Intimate History,[59] was critiqued by geneticists such as Mark Ptashne, at the Memorial Sloan Kettering Cancer Center, and John Greally, at the Albert Einstein College of Medicine, because of over emphasis on histone modification and DNA methylation, while overlooking other important factors. They commented that these two processes have only minor influences in overall gene function. Steven Henikoff, at the Fred Hutchinson Cancer Research Center, opined that, "Mukherjee seemed not to realize that transcription factors occupy the top of the hierarchy of epigenetic information," and said, "histone modifications at most act as cogs in the machinery."[60] It is now generally believed that histone modification and DNA methylations are major factors of epigenetic functions, aging and certain diseases,[61] and with an ability to influence transcription factors.[62] However, they contribute little to development.[63][64] In response, Mukherjee did admit that omission of transcription factors "was an error" on his part.[60]