In 1983, researchers Alan Trounson and Linda Mohr published the article “Human Pregnancy Following Cryopreservation, Thawing and Transfer of an Eight-Cell Embryo,” hereafter “Human Pregnancy,” in the journal Nature. In the article, the authors describe an experiment that led to one of the world’s first pregnancies through cryopreservation, or freezing, of an eight-cell human embryo. They discuss an experiment conducted at the Monash University and Queen Victoria Medical Center in Melbourne, Australia. Prior to the article’s publication, scientists had reported on embryonic cryopreservation experiments with animals only. At the end of the article, the authors mention that the pregnancy ended in a spontaneous miscarriage due to problems unrelated to cryopreservation twenty-four weeks after embryonic transfer. Despite the miscarriage, “Human Pregnancy” is one of the first articles to describe a successful human pregnancy after cryopreservation, and demonstrated that cryopreservation, as part of in vitro fertilization treatment, was a viable option for humans as well.

Susumu Ohno studied chromosome structure and evolution during the twentieth century in the United States. Ohno was one of the first researchers to propose that the Barr body, a mass of genetic material within female mammalian cells, was a condensed X-chromosome. Ohno also developed a theory that gene duplication, when specific regions of a chromosome become multiplied, is a primary driver of evolution, with natural selection playing a secondary role. He theorized that gene duplication allows one copy of the original gene to remain and perform its normal function while a second copy of the gene can mutate and undergo natural selection, leading to diversification of life. Later in his career, Ohno composed music based on DNA sequences. As of 2025, researchers continue to debate Ohno’s theory of gene duplication. Through his research, Ohno introduced a new perspective on the driving forces of evolution, which advanced researchers’ understanding of chromosomal evolution and genetic diversity.

In 1961, Mary Lyon, a researcher who studied genetics, published “Gene Action in the X-chromosome of the Mouse (Mus Musculus L.),” hereafter “Gene Action in the X-chromosome,” in the journal Nature. Lyon’s paper focuses on the workings of female sex chromosomes, or X-chromosomes, and their implications for gene expression. A chromosome is a structure in a cell’s nucleus that contains the DNA, or genetic information, for each individual. In her paper, Lyon proposes her X-inactivation hypothesis, which states that one of the two X-chromosomes in mammalian female cells becomes inactive during early development, silencing its genetic activity. By describing X-chromosome inactivation, Lyon provided an explanation for the mosaic patterns observed in some female mammals, where different regions of their bodies exhibit distinct traits based on the genes carried by the particular X-chromosome that is active in that region. “Gene Action in the X-chromosome” provided evidence that X-chromosome inactivation occurs, laying the basis for understanding sex-linked traits, gene expression, and X-linked genetic diseases that impact thousands of people.