Milestones in Genetics PDF

Milestones in Genetics FISH 147 (FISH GENETICS) https://www.istockphoto.com/photo/zebrafish-aquarium- fish-gm505253725-44563946 Learning Objectives At the end of this lesson, we must be able to: identify and describe key milestones in the...

Milestones in Genetics FISH 147 (FISH GENETICS) https://www.istockphoto.com/photo/zebrafish-aquarium- fish-gm505253725-44563946 Learning Objectives At the end of this lesson, we must be able to: identify and describe key milestones in the field of genetics; gain an understanding of how these milestones shaped our understanding of biology, medicine, agriculture, and other fields; and encourage critical thinking and evaluation of the ethical, social, and scientific implications of milestones in genetic research. Historical Accounts The first evidence that people understood and applied principles of heredity in earlier times is found in the domestication of plants and animals, which began between approximately 10,000 and 12,000 years ago in the Middle East. Historical Accounts Hippocratic School of Medicine "Gemmules” Hereditary traits were drawn from various parts of the male body and passed on through semen (pangenesis) Can be altered and be “passed on” in its altered form Historical Accounts Aristotle Theory of epigenesis Male semen contained “vital heat” with capacity to produce offspring of the same form This heat “cooked” menstrual blood resulting in a “substance” that gave rise to an offspring Historical Accounts Anton van Leeuwenhoek Leeuwenhoek, using his improved microscope, discovered sperm cells, which he initially believed contained miniature humans This observation fueled preformationism Historical Accounts Nicolaas Hartsoeker Preformationism Organisms develop from miniature versions of themselves Instead of assembly from parts, preformationists believed that the form of living things exist, in real terms, prior to their development It suggests that all organisms were created at the same time, and that succeeding generations grow from homunculus Historical Accounts Joseph Gottlieb Kölreuter Conducted extensive plant hybridization experiments Observed that traits from both parents could be passed to offspring and that hybrid offspring could show intermediate traits His primary focus was on the tobacco plant (Nicotiana spp.) Employed artificial fertilization techniques to produce hybrids between different plant species Conducted reciprocal crosses, where he switched the roles of the male and female parents in hybridization experiments Historical Accounts Jean-Baptiste Lamarck Proposed that organisms could modify their bodies through the use or disuse of specific parts Believed that these acquired characteristics, developed during an organism's lifetime, could be passed on to its offspring Postulated that organisms had an inherent tendency to become more complex over time, driven by an internal "force" that directed evolution toward greater perfection. Historical Accounts British naturalist Alfred Russel Wallace originally postulated the theory of evolution by natural selection However, Charles Darwin’s observations during his circumnavigation of the globe aboard the HMS Beagle provided evidence for natural selection and his suggestion that humans and animals shared a common ancestry. Rise of Science in Genetics Nehemiah Grew Reported that plants reproduce sexually by using pollen from the male sex cells With this information, a number of botanists began to experiment with crossing plants and creating hybrids Rise of Science in Genetics Gregor Mendel Father of modern genetics Applied quantitative data analysis for his experiments using pea plants Parents pass traits to their offspring in a predictable manner Each trait is controlled by a pair of “unit factors” which separate during gamete formation Rise of Science in Genetics Gregor Mendel Pea plant experiment Rise of Science in Genetics Robert Brown Described the cell nucleus Building on the work of Brown, Matthias Jakob Schleiden and Theodor Schwann proposed the concepts of the cell theory Early biologists became more interested in heredity and began to examine cells to see what took place in the course of cell reproduction Rise of Science in Genetics August Weismann Demonstrated that the nucleus had a role in fertilization Laid to rest the notion of the inheritance of acquired characteristics He cut off the tails of mice for 22 consecutive generations and showed that the tail length in descendants remained stubbornly long Proposed the germ-plasm theory Rise of Science in Genetics Mendel’s pivotal experiments with pea plants was only rediscovered and gained substantial recognition in 1902 The significance of his conclusions was recognized, and other biologists immediately began to conduct similar genetic studies on mice, chickens, and other organisms Hugo de Vries, Carl Correns, and Erich von Tschermak independently rediscovered Mendel's work, leading to the birth of modern genetics Results of these investigations showed that many traits indeed follow Mendel’s rules Rise of Science in Genetics Walter Sutton and Theodor Boveri The chromosome theory of inheritance, independently developed by Walter Sutton and Theodor Boveri in the early 1900s, is a landmark concept in biology It states that genes, the units of heredity, are located on chromosomes Provided a crucial link between Mendel's laws of inheritance, which described how traits are passed from parents to offspring, and the physical structures within cells responsible for carrying genetic information Rise of Science in Genetics Sutton's Work with Grasshoppers Studied the behavior of chromosomes during meiosis Chromosomes exist in pairs (homologous pairs) in diploid cells During meiosis, homologous chromosomes segregate into different gametes Fertilization restores the diploid number of chromosomes by bringing together chromosomes from each parent The behavior of chromosomes during meiosis mirrored the segregation and independent assortment of Mendel's hereditary factors (genes) Rise of Science in Genetics Boveri's Work with Sea Urchins Demonstrated that a full set of chromosomes is necessary for normal development Different chromosomes carry different hereditary factors Chromosomes maintain their individuality throughout cell division Rise of Science in Genetics Thomas Hunt Morgan Solidified the chromosome theory of inheritance with his experiments in fruit fly (Drosophila melanogaster) Discovered a white-eyed male fly among the typically red-eyed flies Through further crosses, Morgan concluded that the gene for eye color was located on the X chromosome Discovered that some traits tend to be inherited together more frequently than expected by chance Morgan's student, Alfred Sturtevant, developed the first genetic map Morgan's fruit fly experiments revolutionized modern understanding of genetics Rise of Science in Genetics Walther Flemming A pioneer of cytogenetics Observed the division of chromosomes and published a superb description of mitosis At this point, it was generally recognized hat the nucleus contained the hereditary information Birth of Modern Genetics Geneticists began to use bacteria and viruses in the 1940s Rapid reproduction and simple genetic systems of these organisms allowed detailed study of the organization and structure of genes At about this same time, evidence accumulated that DNA was the repository of genetic information Birth of Modern Genetics James Watson and Francis Crick Described the three- dimensional structure of DNA Worked out the chemical structure of DNA and the system by which it determines the amino acid sequence of proteins Birth of Modern Genetics Advances in molecular genetics led to a burst in recombinant DNA experiments starting in 1970s Walter Gilbert and Frederick Sanger developed methods for sequencing DNA in 1977 Polymerase chain reaction was developed by Kary Mullis in 1983 Gene therapy was used for the first time to treat human genetic disease in 1990 Birth of Modern Genetics Advances in molecular genetics led to a burst in recombinant DNA experiments starting in 1970s Human Genome Project was launched in 1990 First complete DNA sequence of a free-living organism (Haemophilus influenzae) was determined First complete sequence of a eukaryotic organism (yeast) was reported in 1996 The Human Genome Project covered about 92% of the total human genome sequence and was completed in 2003 Rapid Advancements in Genetics 2010 - onwards Development of recombinant Genomics DNA technology Next-generation sequencing Cloning and transformation Gene therapy RNAi Gene editing Population genetics Synthetic biology Model Organisms Organisms with characteristics that make them particularly useful for genetic analysis Tremendous amount of genetic information has accumulated Model Organism | Zebrafish Danio rerio as a model organism Concept Checkpoint Would shark make a good model genetic organism? Why or why not? What characteristics should we consider when choosing a model organism?