INTRGEN LE1

• Hippocrates (500 BC) was the Father of Medicine and believed that gods are not responsible for disease
• William Harvey (1578-1657) proposed the theory of epigenesis, contradicting the theory of preformation (homunculus - miniature adult in the egg)
• Preformation


  Fertilized egg contains a complete miniature adult
• Epigenesis


  An organism develops from the fertilized egg by a succession of developmental events that eventually transform the egg into an adult
• The cell theory states that 1) All living things are composed of one or more cells, 2) Cells are the basic units of structure and function in an organism, and 3) Cells come only from pre-existing cells
• The theory of spontaneous generation was debunked with the formation of the cell theory
• Cell


  Has its job and function, where life starts, and organisms will eventually have to adapt to the environment
• Charles Darwin published On the Origin of Species in 1859, describing ideas about evolution and natural selection

  
• Natural selection


  Populations tend to produce more offspring than the environment can support, leading to a struggle for survival. Those individuals with heritable traits that allow them to adapt to their environment are better able to survive and reproduce than those with less adaptive traits. If a population carrying these inherited variations becomes reproductively isolated, a new species may result.
• Darwin lacked an understanding of the genetic basis of variation and inheritance, which left his theory open to reasonable criticism well into the 20th century
• Gregor Mendel published a paper in 1866 showing how "traits" were passed from generation to generation in pea plants, which was not popularly known until it was duplicated in studies around 1900
• The scientists Carl Correns, Hugo de Vries, and Erich Tschermak played a crucial role in establishing Mendelian genetics as the basis for understanding the principles of heredity, paving the way for the development of modern genetics
• Chromosomal theory of inheritance


  • Identified chromosomes, diploid number, homologous chromosomes, cell division (mitosis and meiosis), and haploid number. Inherited traits are controlled by genes residing on chromosomes faithfully transmitted through gametes, maintaining continuity from generation to generation.
• Genetic variation


  Mutations are defined as any heritable change in the DNA sequence and are the source of all genetic variation
• Walter Sutton proposed the theory of inheritance, hypothesizing that the segregation and assortment of chromosomes during cell division could explain the transmission of traits from parents to offspring
• Theodor Boveri studied the roles of chromosomes in cell division and heredity

  
• Thomas Hunt Morgan's experiments with Drosophila provided strong evidence that genes are located on chromosomes and that their arrangement of chromosomes influence inheritance patterns
• In the 1920s, scientists knew that proteins and DNA were major components of chromosomes, and many researchers thought proteins carried genetic information
• The discovery of the DNA double helix by Watson and Crick launched the era of molecular genetics
• DNA


  Lacks a hydroxyl group in one of the sugars, with C-G pairing having 3 hydrogen bonds and A-T pairing having 2 hydrogen bonds
• RNA


  In the form of a loop, not a strand
• RNA has an important role in regulating the expression of genes
• Promoter


  Decides when and how many genes will be expressed
• Response elements


  Collects RNA polymerase, lets it attach itself, and drives the expression of the gene

  
• DNA in roots, leaves, and fruits has the same set of genes, but some genes are expressed in some areas only as regulated by the promoter

  
• The purpose of DNA cloning is to provide food for the rapidly growing population
• Criteria for model organisms


  • Genetic traceability, short generation time, small size, available and easy to maintain, similarity to humans or target organism, well-defined genome/annotated, ethical considerations, research history
• Cytogenetics


  Karyotyping - looking at the different chromosomes, using dye to specify different chromosomes

  
• Transmission genetics


  Breeding and pedigree, traits can be passed on to offspring
• Quantitative genetics


  Breeding and selection, looking for parts of genetics that can be quantified in a controlled environment, e.g. predicting number of harvest
• Key concepts and principles of quantitative genetics


  • Polygenic inheritance
  • Influence of environment
  • Heritability
  • Phenotypic variation
  • Breeding and selection
  • Quantitative trait loci (QTL)
• Population genetics


  Studies the genetic composition of populations and how it changes over time
• Cell Division


  An integral part of the cell cycle, results in genetically identical daughter cells, cells duplicate their genetic material before division

  
• Phases of the Cell Cycle

  1. Interphase

  2. Mitotic Phase

  
• Interphase


  • Normal cell activity that precedes mitosis, longer than mitotic phase, cell grows and produces proteins required by the daughter cells, most number of cells under a microscope

  
• G1 phase


  Prepares the materials needed in the S phase, cellular contents are duplicated except for chromosomes

  
• S phase


  Actual duplication of the genetic material - DNA replication, occupies more volume

  
• G2 phase


  Critical point where DNA is checked for errors, which are repaired, too many errors/mutations → cell lysis or apoptosis (programmed cell death)

  
• Checkpoints


  • G1 to S phase: growth factors, nutrients, size
  • End of G2 phase before committing to proceeding to mitosis: cell size, duplicated DNA, DNA damage

  
• Mitotic Phase


  Telophase cell - cell division, cytokinesis - other materials other than nuclear material is synthesized such that the cell will become fully grown