Some diseases are transmitted only from parents to children. Hemophilia is a well-known example. All living beings have their properties coded in genes DNA on the chromosomes in the nucleus of every single cell. Chromosomal and Mitochondrial DNA analysis is able to provide strong evidence in proving or refuting close bloodrelationship through females among individuals. History Demographers are interested in the extent of populations in the past.
Social historians are interested in the evolution of living conditions.
All these historians often consult the same historical sources as genealogists do. Genetics and Heredit ariness Genetics is the scientific study of how physical, biochemical, and behavioral traits are transmitted from parents to their offspring. Geneticists are able to determine the mechanisms of inheritance because the offspring of sexually reproducing organisms do not exactly resemble their parents, and because some of the differences and similarities between parents and offspring recur from generation to generation in repeated patterns. The science of genetics began in 1900, when several plant breeders independently discovered the work of the Austrian monk Gregor Mendel, which, although published in 1866, had been virtually ignored. Working with garden peas, Mendel described the patterns of inheritance in terms of seven pairs of contrasting traits that appeared in different pea-plant varieties.