Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. Though heredity had been observed for millennia, Gregor Mendel, a scientist and Augustinian friar working in the 19th century, was the first to study genetics scientifically. Mendel studied 'trait inheritance', patterns in the way. And the Medical Genetics and Genomics Program provides risk assessment, genetic counseling and, when appropriate, genetic testing for the many different conditions that can run in families. These can range from bleeding and blot-clotting disorders to diseases of the skin, kidney, lung and eye. Genetics is devoted to the study and manipulation of heredity and variation in living organisms.

Evelyn Fox Keller dubbed the 1900s the “century of thegene”, and for good reason (Fox Keller 2002). During a 100-yearspan that opened with excitement about the research Mendel conducteddecades earlier and closed with the Human Genome Project, disciplinesranging from comparative anatomy to oncology were infused with geneticconcepts, genetic principles, and genetic methodologies. The first twodecades of the twenty-first century have seen this trend onlyexpand.

Genetics A key to the mystery of fast-evolving genes was found in ‘junk DNA’ A new study challenges a long-held belief that essential genes change little over time. Genetics and Plant Breeding or Master of Science in Genetics and Plant Breeding is a postgraduate Plant Pathology course. The program is truly interdisciplinary, with membership from agronomy, biochemistry, botany, forest and wildlife ecology, genetics, horticulture, plant pathology, and statistics. Plant Breeding is the science and art of improving crop plants through the study and application of genetics.

So it should not be surprising that philosophers have gravitated togenetics in an attempt to understand how that science works, what itsays about the world, and what impact it has on people living in asociety where there is so much focus on genes. This encyclopediarepresents well this significant philosophical interest. Over 100entries discuss some aspect of genetics, and those entries engage awide range of philosophical questions—questions about scientificexplanation, questions about the process of evolution, questions aboutdisability, questions about race. With such diverse philosophicalinterest in genetics, no single encyclopedia entry could do justice tothe full scope of that science and the rich philosophical attention ithas received. Instead, this entry serves as a door into thatphilosophical world. After a historically-guided introduction to thescience of genetics and its transformative impact, the piece reviews asample of the philosophical questions that genetics has generated,with direction to entries where those topics are discussed in greaterdetail. The hope is that the entry will serve as an orientation to thediversity of philosophical thought concerning genetics that isdistributed throughout the encyclopedia. (The entry on evolution provides a similar guide to the trove of entries that reviewphilosophical discussions around that topic.)

1. The Science of Genetics
2. Philosophical Questions about Genetics

1. The Science of Genetics

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Genetics is devoted to the study and manipulation of heredity andvariation in living organisms. Genetics is so pervasive intwenty-first century science—in reproductive screeningtechnologies like preimplantation genetic diagnosis, in assessments ofwhat species are endangered, in public health programs that trackantibiotic-resistant bacteria, to name a few—that it is easy toforget what these disparate practices all have in common with oneanother: a focus on the patterns and mechanisms of trait transmissionfrom one generation to the next in order to understand and potentiallycontrol that process. This contemporary focus can be traced back tothe first years of the twentieth century, when genetics took shape asa unique field of study.

1.1 Birth of a Discipline

Gregor Mendel, the Austrian monk now commonly referred to as the“father of genetics”, never uttered the terms“gene” or “genetics” because those termsweren’t introduced until decades after his death. In 1865, hereported on the results of breeding experiments he performedhybridizing pea plants during which he tracked how a series of traits(e.g., round vs. wrinkled peas, white vs. purple flowers) passed downthrough generations. Mendel noted certain patterns of inheritance; forexample, traits seemed to be transmitted independently of one another(Mendel 1866). Mendel died in 1884, at which point there was littleindication that he would end up in biology textbooks (Olby 1985).

It wasn’t until 1900 that the full force of Mendel’sobservations became absorbed by the scientific community. That year,three different European botanists reported on the results of theirown breeding experiments and linked their results back toMendel’s work decades earlier. Mendel’s research, at thistime, was characterized as revealing heredity to involve thetransmission of discrete hereditary factors that obeyed fundamentalprinciples—that organisms get one copy of each factor from eachparent and, in turn, pass one copy on to their own offspring (the lawof segregation), that the factors segregate independently of oneanother (the law of independent assortment), and that certain factorsdominate other factors when it comes to expressing the traitassociated with that factor (the law of dominance) (entry: gene). William Bateson, a biologist at the University of Cambridge at thetime, was excited about the implications of Mendel’s work fortheories of evolution; he recruited a number of youngscientists—women in particular—to Cambridge to performexperiments showing that Mendel’s principles extended across theplant and animal kingdoms (Richmond 2001). He called this newdiscipline “genetics”, and “gene” became theterm for the factor that was inherited (entry: the genotype/phenotype distinction).

With genetics carved out as a unique field of study, two threads ofgenetic research ensued. One thread focused on identifying thephysical unit of heredity that was passed from generation togeneration—to figure out what genes were, where they werelocated, how they operated, and how that operation produced thehereditary patterns consistent with Mendel’s principles (entry: epigenesis and preformationism). Thomas Hunt Morgan’s research at Columbia University mostcontributed to this work. Morgan studied fruit flies, in part becausethey bred quickly and were easy to maintain. With a team of youngscientists, he crossed thousands upon thousands of fruit flies,tracking how traits like eye color and wing shape transmitted acrossgenerations. They also induced mutations using a variety of chemicaland radiation interventions (see the entry on experiment in biology). This research proved that genes were located on chromosomes, and itshowed how the physics of chromosomal action during meiosis impactedthe hereditary process; for example, genes closer together onchromosomes were more often inherited together, while genes that werefurther apart more often separated from one another during chromosomalrecombination. This realization allowed Morgan and his students toproduce the first gene maps—charts of genes’ relativelocations to one another—and also determine that certain traitswere sex-linked due to their location on sex chromosomes (Darden 1991;Kohler 1994).

The other thread of genetic research that emerged attended to theevolutionary implications of Mendelian inheritance. Charles Darwinpublished On the Origin of Species in 1859, and the fact ofevolution was widely recognized by 1900; however, the nature of theevolutionary process remained contested (Darwin 1859). According toDarwin, evolution was a very slow and gradual process, with naturalselection favoring subtle differences between organisms (slightlylonger legs, for example) that inclined one to be more successful atreproduction in some particular environment (entry: Darwinism). Mendel’s principles of inheritance, when they were hailed atthe turn of the twentieth century, were thought by many geneticists tobe incompatible with Darwinian evolution because Mendelian inheritanceseemed more discrete (e.g., round or wrinkled peas, purpleor white flowers), and so it was favored by scientists whoadvocated for a faster and more discontinuous process of evolution.Indeed, one of the reasons that Bateson so eagerly championedMendel’s work was because he was a propo

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