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LECTURE CONNECTIONS 1 | Introduction to Genetics © 2009 W. H. Freeman and Company Hopi Native Americans • Albinism, a genetic condition, arises with high frequency among the Hopi people and occupies a special place in the Hopi culture (1 in 200 people). • Albinism is caused by defects in any of the 4 genes that control the synthesis and storage of melanin. • Why is albinism so frequent among the Hopi Native Americans? Introduction to Genetics • The importance of genetics: - Albinism in the Hopi Native Americans: genetics altered the occupation, the role in Hopi society, and relations with other members of the tribe. - Genes affect our height, weight, hair color, skin pigmentation, etc. - Genes can influence our susceptibility to many diseases and disorders. - Genes contribute to our intelligence and personality; - Agriculture; - Domestication of plants and animals; - Pharmaceutical industry: drugs and food additives are synthesized by fungi and bacteria that have been genetically manipulated to make them efficient producers of these substances. Examples: growth hormone, insulin and clotting factor. - Genetics play a critical role in medicine (sickle-cell anemia); - Gene therapy; - Evolution: is the genetic change taking place through time; - Taxonomy, ecology, and animal behavior are making increasing use of genetic methods; - Developmental Biology: tissues and organs form through the regulated expression of genes. Genome • Genome is a complete set of genetics instructions for any organism. • All genomes are encoded in nuclei acids- either DNA or RNA. • Genetic variation is the foundation of all evolutionary change and is ultimately the basis of all life as we know it. • Genetics: past, present and future. Division of Genetics • Transmission genetics: relation between chromosomes and heredity. • Molecular genetics: chemical nature of the gene itself. • Population genetics: genetic composition of individual members of the same species. Model Genetic Organisms • Model organisms are organisms with characteristics that make them useful for genetics analysis: • Common characteristics of model organisms: - Short generation time; - Large but manageable number of progeny; - Adaptable to laboratory environment (can be housed and propagated inexpensively). The history of Genetics Organisms • First evidence that people understand hereditary: 10,000-12,000 years ago in the domestication of plants and animals; • Greeks (520 B.C.): concept of pangenesis and inheritance of acquired charasteristics. • Aristotle (384-322 B.C.) believed that both males and females made contributions to the offspring. • In 1665, Robert Hooke discovered cells and gave scientists the idea of preformationism (all traits would be inherited from only one parent). • Blending inheritance: offsprings are a blend. • In 1676, Nehemiah Grew reported that plants reproduce sexually by using pollen from the male sex cells. • Gregor Mendel discovered the basic principles of hereditary in 1866. • In 1859, Charles Darwin put forth the theory of evolution through natural selection and recognized that heredity was fundamental for evolution. Fundamental terms and principles of genetics • 2 basic types of cells: - Prokaryotic: lack a nuclear membrane and possess no membrane-bounded cell organelles - Eukaryotic: more complex, possessing a nucleus and membrane-bounded organelles such as chloroplasts and mitochondria • The gene is the fundamental unit of heredity • Genes come in multiple forms called alleles • Genes confer phenotypes and genetic information is the genotype • Genetic information is carried in DNA and RNA Nuclei acids are polymers consisting of repeating units called nucleotides; each nucleotide consists of sugar, a phosphate, and a nitrogenous base (DNA: A, C, G and T; RNA: A, C, G and U). • Genes are located in chromosomes • Chromosomes separate through the processes of mitosis and meiosis • Genetic information is transferred from DNA to RNA to protein • Mutations are permanent • Some traits are affected by multiple factors • Evolution is genetic change