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After an organism dies, most of its cells begin to extinguish activity and die shortly afterward. However, other cells exhibit a curious behavior. Instead of winding down their operations, certain gene activities resurrect.1

          Image of cells dividing and a human embryo 

Low Oxygen Beginnings

During the earliest stages of embryonic development, stem cells proliferate in a low oxygen environment. The genes that drive this stage are active for a short period of time. After the blastocyst implants into the uterus, eventually, oxygen levels increase and gene activity that was previously maintained by low oxygen levels silences.2,3

Survival Instinct

Cellular life after death may seem paradoxical, but sudden changes in oxygen levels trigger protective responses in cells. Genes that are transcribed during the low oxygen phase of embryonic development are reactivated when oxygen levels plumet after organismal death. Many emergency-mode genes also activate to support cell survival, including those involved in inflammation, immunity, stress responses, and cancer. Scientists studied this in zebrafish and mice, as well as human blood, prostate, liver, and brain tissue samples.1,4,5,6,7

          Illustration of a human combined with DNA and a hand holding DNA strands
          Illustration of a magnifying glass over a human chest

Real-world Zombie Genes

There are practical applications for understanding why and how genes are activated after death. For example, forensic scientists apply insights from postmortem gene transcription to estimate the time of death in criminal cases. Scientists also use information about cancer gene reactivation to improve organ transplant outcomes. Performing transplant surgery before these genes become active may help reduce the high incidence of cancer in organ transplant recipients.8

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