THE BIOLOGY BOOK
Jean-Baptiste Lamarck (1744–1829)
Two centuries ago, Jean-Baptiste Lamarck postulated that environmental factors could influence traits, which could be transmitted to offspring. This theory was soundly rejected during his lifetime. Based on animal and human studies, scientists are now having second thoughts.
Almost six decades after the World War II Hongerwinter (hunger winter), survivors exhibited abnormal patterns of methylation that turn on or off genes associated with a number of disorders. The Hongerwinter in Holland began late during 1944, when food supplies were so drastically cut that they provided less than one-quarter of the recommended daily intake. This continued until the liberation of Holland in May 1945; 18,000–22,000 starved to death. The children conceived during this period were small, underweight, and, compared to their siblings conceived before and after the famine, at greater risk of obesity, heart disease, diabetes, and hypertension. Similar results were seen in children after the 1968–1970 Biafra famine in Nigeria. Individuals prenatally exposed to maternal food deprivation during the Great Chinese Famine (1958–1961) showed an increased risk of schizophrenia.
Traits are determined by genes—information carried by DNA. DNA dictates the manufacture of proteins and RNA molecules, which is translated to the manufacture of proteins, the link between our genetic makeup and our outward or physical traits. Epigenetics refers to all changes to genes other than changes in the DNA sequence. Such epigenetic changes commonly include the addition of methyl (–CH3) groups to the DNA backbone, “marking” the DNA, and interfering with its ability to transcribe messages to RNA. Epigenetic marks have also been seen in some cancers.
In 2012, Andrew Feinberg reported differences in DNA methylation patterns in female worker bees who, within a hive, share identical genetic sequences but exhibit different behavioral patterns. Some remain in the hive and nurse the queen, and, upon maturity, leave the hive and forage for pollen. Nursing and foraging bees each have their own distinct DNA methylation patterns. When nurse bees were removed from the hive, the foragers stepped in to replace them, and their methylation patterns changed to that seen with nurse bees. Hence, epigenetic “marks” are reversible and linked to behavior.
SEE ALSO: Larmarckian Inheritance (1809), Mendelian Inheritance (1866), Genetics Rediscovered (1900), Genes on Chromosomes (1910), DNA as Carrier of Genetic Information (1944).
Differences in DNA methylation patterns have been found between genetically identical nursing and foraging female worker bees, suggesting that behavior can alter gene expression.