[1]  He then resumed work as a research associate with Daniel Mazia at the University of California, Berkeley, and ultimately earned a PhD in biochemistry in 1967.

[4] Loeb made major contributions to the understanding the fidelity of DNA synthesis, and developed the first methods for quantitating error rates in that process.

[3]  Loeb has used such techniques to assess the fidelity of various DNA polymerases and to investigate the effects of environmental and chemical carcinogenesis, as well as mutagenesis induced by metal ions and by oxygen-free radicals.

[4][7][2][8]  This hypothesis posits that, because malignant cells exhibit defects in the fidelity of DNA replication, large numbers of mutations accumulate genome wide as they divide during tumor progression.

[7]  This phenotype results in a heterogeneous population of cancer cells and lineages within a tumor, wherein individual clones may display different attributes that contribute to the fitness of a tumor, such as resistance to radiation or chemotherapy, or the ability of cancer cells to metastasize or disseminate.