GENETICS A Conceptual Approach CHAPTER 1 INTRODUCTION TO GENETICS Royal Hemophilia and Romanov DNA Hemophilia results from a genetic deficiency of blood clotting o Marked by slow clotting and excessive bleeding o One of the factors in the clotting cascade is missing or faulty Females may be unaffected carriers of the gene for hemophilia on their X chromosome if they have one normal X chromosome and one defective one o A female exhibits hemophilia only if she inherits two defective copies Males only have one X chromosome so if they inherit a defective copy they develop hemophilia o More common in males than females The bodies of the Russian tsar and his family were confirmed to be just that using mitochondrial DNA o Mitochondrial DNA is inherited only from the mother o Mitochondrial DNA was extracted from the bones and amplified with PCR The Importance of Genetics Genes influence o Height o Weight o Hair color o Skin pigmentation o Susceptibility to diseases and disorders o Intelligence o Personality Genetics is used in and have desirable traits Disease resistance Pest resistance Special nutritional qualities Qualities that facilitate harvest o Pharmaceuticals synthesizing drugs with fungi and bacteria o Medicine insight into genetic disorders and diseases and gene therapy The Role of Genetics in Biology All organisms use the same genetic system Evolution genetic change taking place through time o Agriculture domestication of plants and animals to increase yields Developmental biology tissues and organs form through the regulated expression of genes Other areas of biology in which genetics are used o Taxonomy o Ecology o Animal behavior Genetic Diversity and Evolution Genome Life is characterized by adaptation a complete set of genetic instructions for any organism Genetic instructions are in the same format and with rare exceptions the o Encoded in nucleic acids code words are identical The process by which genetic information is copied and decoded is remarkably similar for all forms of life o Suggests that all life on Earth evolved from the same primordial ancestor that arose between 3 5 billion and 4 billion years ago The all organisms have a common genetic system means o The study of one organism s genes reveals principles that apply to other organisms o Genes will function in foreign cells genetic engineering o Basis for diseases such as AIDS Life s diversity and adaptation are products of evolution o Genetic variants arise randomly o The proportion of particular variants increases or decreases Genetics the study of genetic variation o Genetic variation is the basis of all evolutionary change Divisions of Genetics Three major subdisciplines o Transmission genetics are passed from one generation to the next the basic principles of genetics and how traits The relation between chromosomes and heredity The arrangement of genes on chromosomes Gene mapping Focused on the individual organism o Molecular genetics concerns the chemical nature of the gene itself How genetic information is encoded replicated and expressed Replication transcription and translation processes by which genetic information is transferred from one molecule to another Gene regulation the processes that control the expression of genetic information Focused on the structure organization and function of the gene o Population genetics explores the genetic composition of groups of individual members of the same species and how that composition changes over time and geographic space The study of evolution Focused on a group of genes found in a population The three fields overlap and have their own subdivisions o Chromosomal genetics o Biochemical genetics o Quantitative genetics Model Genetic Organisms Model genetic organisms particularly useful for genetic analysis and about which a tremendous amount of genetic information has accumulated organisms with characteristics that make them o Examples Escherichia coli bacteria present in the gut of humans and other mammals Saccharomyces cervisiae baker s yeast Arabidopsis thaliana a mustard plant Caenorhabditis elegans a nematode worm Drosophila melanogaster the fruit fly Mus musculus the house mouse Neurospora crassa bread mold Danio rerio zebra fish Xenopus laevis clawed frog Zea mays corn Model organisms possess traits and life cycles that make them particularly suitable for genetic study o Short generation time o Manageable numbers of progeny o Adaptability to a laboratory environment o Ability to be housed and propagated inexpensively A Brief History of Genetics Prehistory First evidence that people understood and applied the principles of heredity is the domestication of plants and animals about 10 000 12 000 years ago The world s first agriculture is thought to have developed in the Middle East as a result of domestication Early Written Records Ancient writings indicate that humans were aware of their own heredity specific particles called gemmules carry information from Pangenesis various parts of the body to the reproductive organs from where they are passed to the embryo at the moment of conception o Persisted until the late 1800s Inheritance of acquired characteristics traits acquired during one s lifetime become incorporated into one s hereditary information and are passed on to offspring o Popular through the twentieth century The Rise of Genetics Microscopes gave rise to preformationism inside the egg or sperm exists a tiny miniature adult a homunculus which simply enlarges during development o All traits would be inherited from one parent Blending inheritance Gregor Mendel discovered the basic principles of heredity and is recognized offspring are a blend or mixture of parental traits as the father of genetics Cell theory cells and the cell is the fundamental unit of structure and function in living organisms all life is composed of cells cells arise only from preexisting o Proposed by Matthias Jacob Schleiden and Theodor Schwann in 1839 Walther Flemming observed the division of chromosomes in 1879 and published a description of mitosis By 1885 it was recognized that the nucleus contained the hereditary Germ plasm theory information set of genetic information that is passed to the egg and sperm the cells in the reproductive organs carry a complete o Proposed by August Weismann at the end of the nineteenth century who disproved inheritance of acquired characteristics by cutting the tails off of mice for 22 generations Modern Genetics 1910 Walter Sutton