An introduction to population genetics theory and applications pdf
This is the latest accepted revision, reviewed on 23 March 2018. This article is about the general scientific term. An introduction to population genetics theory and applications pdf a more accessible and less technical introduction to this topic, see Introduction to genetics. Genetics is the study of genes, genetic variation, and heredity in living organisms.
The father of genetics is Gregor Mendel, a late 19th-century scientist and Augustinian friar. Mendel studied “trait inheritance”, patterns in the way traits are handed down from parents to offspring. Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded beyond inheritance to studying the function and behavior of genes. Genetic processes work in combination with an organism’s environment and experiences to influence development and behavior, often referred to as nature versus nurture. The observation that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. Prior to Mendel, Imre Festetics, a Hungarian noble, who lived in Kőszeg before Mendel, was the first who used the word “genetics. His second law is the same as what Mendel published.
Blending inheritance leads to the averaging out of every characteristic, which as the engineer Fleeming Jenkin pointed out, makes evolution by natural selection impossible. Other theories of inheritance preceded Mendel’s work. A popular theory during the 19th century, and implied by Charles Darwin’s 1859 On the Origin of Species, was blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents. Morgan’s observation of sex-linked inheritance of a mutation causing white eyes in Drosophila led him to the hypothesis that genes are located upon chromosomes. Modern genetics started with Mendel’s studies of the nature of inheritance in plants. The importance of Mendel’s work did not gain wide understanding until 1900, after his death, when Hugo de Vries and other scientists rediscovered his research. After the rediscovery of Mendel’s work, scientists tried to determine which molecules in the cell were responsible for inheritance.
DNA, the molecular basis for biological inheritance. Each strand of DNA is a chain of nucleotides, matching each other in the center to form what look like rungs on a twisted ladder. Although genes were known to exist on chromosomes, chromosomes are composed of both protein and DNA, and scientists did not know which of the two is responsible for inheritance. Although the structure of DNA showed how inheritance works, it was still not known how DNA influences the behavior of cells. In the following years, scientists tried to understand how DNA controls the process of protein production. With the newfound molecular understanding of inheritance came an explosion of research.
At its most fundamental level, inheritance in organisms occurs by passing discrete heritable units, called genes, from parents to offspring. In the case of the pea, which is a diploid species, each individual plant has two copies of each gene, one copy inherited from each parent. Many species, including humans, have this pattern of inheritance. The set of alleles for a given organism is called its genotype, while the observable traits of the organism are called its phenotype. When a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent. These observations of discrete inheritance and the segregation of alleles are collectively known as Mendel’s first law or the Law of Segregation.