She grew up on a farm in rural southeastern Michigan, complete with a 1-room schoolhouse. She was entranced by the beautiful flowers and vegetables her family grew, as well as with the apples and other fruits from their orchard. This tranquil rural life transmitted to her a great love and appreciation of all the life she saw around her, propelling her into the study of the deepest depths of nature, genetics, which she helped revolutionize after leaving the farm.

Dr. Lynn Sorensen Ripley passed away from sudden heart failure at the age of 78 at her home in New York City on December 1, 2024. She was preceded in death by her parents, Earl and Phyillis Sorensen, as well as her sister Dr. Gail Sorensen. Her former husband, David Ripley, preceded her in death earlier in 2024.

Lynn grew up in Ganges Township near Fennville, Michigan, attending that 1-room schoolhouse. She excelled academically, winning a science award while in high school that enabled her to spend a summer in the late 1960s in the laboratory of Dr. David Pittman at Southern Illinois University in Carbondale, IL. There she learned microbiology and, most importantly, microbial genetics. She knew she would be leaving the farm.

That experience ignited her life-long interest in genetics, which she studied at Michigan State University in East Lansing, MI, where she obtained her bachelor's degree in biology in 1968. She did her PhD in genetics in the laboratory of John Drake at the University of Illinois in Champaign-Urbana, IL. Afterwards, she did a postdoctoral fellowship with Drake when he moved to the National Institute of Environmental Health Sciences (NIEHS), one of the institutes of the National Institutes of Health, in Research Triangle Park, North Carolina. In 1985, she joined the faculty of the Rutgers School of Medicine in Newark, New Jersey, where she did research and taught microbiology and genetics to medical students until her retirement.

While at NIEHS, she began her seminal work on mutational mechanisms. Organisms make mutations in DNA all the time; and when one cannot ascribe a cause for them, they are called spontaneous mutations. In a series of papers starting in 1982, Lynn proposed a startling mechanism to explain how some spontaneous mutations occurred. She suggested that when DNA was single-stranded during DNA replication, stretches of DNA that had quasi-palindromic (imperfect inverted repeated) sequences of nucleotides could fold to form hairpin loops. These could then be processed by the cell to form deletion or duplication mutations in DNA. It was an audacious idea that took several years to be accepted by the genetics community.

In subsequent years, she showed how this process also resulted in insertion mutations, where a small stretch of DNA sequence was inserted seemingly randomly into the DNA. She demonstrated that the inserted sequence was, in fact, templated (coded) by a nearby sequence that was complimentary to the inserted sequence and was brought to the site of insertion by the hairpin loop. In other words, the new inserted sequence of nucleotides did not come out of nowhere, it was coded for by a nearby sequence. She also showed that hairpin loops of DNA also caused what she called concerted mutations, which were a cluster of mutations that occurred all at once within a region of DNA. Prior to her discovery of this mechanism, such clusters of mutations were thought to occur independently somehow, one at a time.

If this was not enough, she had one more discovery that revealed the magic of mutagenesis. In 1988, she published the first of several papers identifying a mutational mechanism by which certain chemical mutagens called frameshift mutagens caused mutations. She demonstrated that these mutagens worked in concert with enzymes called topoisomerases. These enzymes normally release torsional stress in a twisted DNA molecule by cutting the DNA, allowing the strands of DNA to rotate to relieve the stress, and then re-connecting the strands.

Lynn showed that when frameshift mutagens were associated with DNA at sites where these enzymes normally cut DNA, the chemical mutagen blocked the enzyme from reconnecting the cut pieces of DNA, resulting in deletion or duplication mutations in the DNA. Prior to this, repeated DNA sequences were thought to be required for such mutations to occur, without the intervention of an enzyme. Her discovery explained how a set of highly mutagenic anti-cancer drugs called topoisomerase inhibitors caused mutations and cytotoxicity, resulting in the death of fast-replicating cancer cells.

Lynn's discoveries in the field of mutagenesis are now in textbooks and are the legacy of her remarkable scientific career. Along with being a brilliant geneticist, Lynn was an excellent teacher of medical students, an outstanding cook, and a wine connoisseur. Upon retirement, she joined food- and wine-tasting clubs in New York City, learned to cook a variety of cuisines, and applied her scientific expertise to cooking, producing unique dishes combining unusual ingredients.

From the roof of her brownstone in New York City, she recreated in miniature the Michigan farm on which she had spent her childhood, growing beautiful tomatoes, peppers, squash, etc. in large pots in the middle of Manhattan, just one block from Central Park across from the Museum of Natural History. Her love of nature and food converged when she sat in her roof-top garden on a warm summer evening with a glass of wine and a beautiful meal, contemplating the mysteries of mutation playing out in the wonderous nature below her in Central Park.