Cytogen

• Heredity: passing of traits and biological processes in between generations
• Genes: ○ Center of study ○ Unit of heredity ○ Segment of DNA
• Cytogenetics: study of chromosomes
• Cytology: study of cells
• Genetics: study of inherited variation
• 3 Categories of Traits ● Morphological ● Physiological ● Behavioral
• Examples of Genetic Variation (within species) ● Domesticated species ● Human genetics ● Natural populations
• Phenotypic variation is a direct consequence of genetic variation
• Primary Sources ● Mutations ● Gene flow

  ● Sex
• Mutations: changes in DNA
• Gene flow: movement of genes from one population to another
• Sex: can introduce new gene combinations; genetic shuffling
• CLASSICAL GENETICS ○ Chromosomal theory of inheritance: the concept that genes are located linear in chromosomes ○ Based on Gregor Mendel’s 1st and 2nd Law ■ Law of Segregation ■ Law of Independent Assortment
• MOLECULAR GENETICS ○ Based on the central dogma
• EVOLUTIONARY GENETICS ○ Theory of Natural Selection by Charles Darwin ○ Changes in gene frequencies in populations
• People have known about inheritance for a long time. ○ children resemble their parents ○ domestication of animals and plants, selective breeding for good characteristics ○ Sumerian horse breeding records ○ Egyptian data palm breeding ○ Bible and hemophilia
• 3 NOTABLE DISCOVERIES ● Light microscopy ● Cell theory ● Charles Darwin’s Origin of Species ○ Theory of evolution by natural selection
• Robert Hooke ● Coined the term “cell” by studying about corks
• Anton Van Leeuwenhoek ● Single lens microscope ● Discovered protozoa and bacteria in rainwater
• Charles Darwin ● published The Origin of Species, which describes the theory of evolution by natural selection
• Gregor Mendel ● Published Experiments in Plant Hybridization (using pea plants) which lays out the basic theory of genetics ○ It was widely ignored until 1900 ○ The basic theory of genetics led to the discovery of chromosomes and their behavior
• Friedrich Miescher ● – isolated “nuclein” from pus cells (WBCs) ● Discovered DNA as a distinct molecule
• Ernst Haeckel ● The experiments of Ernst Haeckel proved that the genetic material is indeed located in the nucleus
• 1900 ● rediscovery of Mendel’s work by Carl Correns, Hugo de Vries, and Erich von Tschermak.
• Archibald Garrod discovered that alkaptonuria, a human disease, has a genetic basis.
• Alkaptonuria: a genetic metabolic disorder caused by the accumulation of homogentisic acid because HGD Gene (Homogentisic Acid Gene)
• Walter Sutton - hypothesized that the behavior of chromosomes during meiosis, thus leading to the discovery that genes are located on chromosomes
• Wilhelm Johannsen ● - coined “gene”
• William Bateson discovered linkage between genes. Also coins the word “genetics”. - Genetics: “genno” Greek word means to give

  birth
• Reginald Punnett and Bateson discovered the science of genetic linkage. ○ They also coined the term “epistasis” to describe the interaction between two different traits
• Epistasis: if two genes are present, a certain gene will make the expression of the other one
• Thomas Hunt Morgan proved that genes are located on the chromosomes using Drosophila, a fruit fly.
• Hermann J. Muller - shows that X-rays induce mutations
• Oswald Avery, Colin MacLeod and Maclyn McCarty - showed that DNA can transform bacteria, demonstrating that DNA is the hereditary material
• James Watson and Francis Crick determine the structure of the DNA molecule, which leads directly to knowledge of how it replicates ○ Discovered the secondary structure of DNA - double helix
• Marshall Nirenberg solves the genetic code, showing that 3 DNA bases code for one amino acid ○ There are 64 possible codons, ○ 3 do not code for amino acid (stop codons: UAA, UGA, UAG) ○ Start codon: AUG
• Reverse transcriptase - an enzyme found in retroviruses, was discovered and was used in cloning genes
• Paul Berg = 1st to create a recombinant DNA mole
• Stanley Cohen and Herbert Boyer combine DNA from two different species in vitro, then transform it into bacterial cells: first DNA cloning
• Frederick Sanger - introduced (set of genes of an organism) of a bacteriophage