Cyto midterm

• Genetics


  The branch of biology that deals with heredity and variation
• Gene


  At molecular level, a segment of DNA that has the information to produce a functional product
• Today, human genetics is for everyone; more about variations than illnesses
• Once an obscure science or an occasional explanation for an odd collection of symptoms, human genetics is now part of everyday conversation
• Human genetics is now being recognized as one of the bases for medical science
• Genetic knowledge


  Informative and empowering as it allows us to control our environment
• Genetics


  • Centered on the study of genes
  • Deals with inherited traits, their variations, and sometimes confused with genealogy
• Inherited traits range from obvious physical characteristics to talents, behavior, and difficult to define characteristics
• Inherited traits may reflect a combination of genetic and environmental influences
• Until the 1990s, genetics was more academic than clinical science except for inherited diseases that show a clear pattern in the family
• As the century passed, researchers completed projects such as the global human genome, where it was discovered that there was in fact a complete set of genetic instructions
• Today genetics has emerged as informational and as a life science that has a huge societal impact
• The genetic information is now accessible to anyone
• The contribution of genes to the most common traits and disorders are appreciated
• Genetics has its own vocabulary which has precise definitions

  All concepts are merely introductions that sets the stage for us to have details in sequence as we go along in studying the concept of genes
• Methods of Genetic Study

  • Pedigree Analysis
  • Karyotyping
  • Planned Experimental Breeding
  • Twin Study
  • Statistical Analysis
• Trait


  A specific characteristic that varies from one individual to another
• Genotype


  The allelic constitution/genes of an organism
• Phenotype


  The morphological, biochemical, behavioral, or other properties of an organism, observe the transmission of traits to the next generation
• Alleles


  The different possibilities for a given trait. Every trait has at least two alleles (one from the mother and one from the father)
• Types of Alleles


  • Homozygous
  • Heterozygous
• Dominant gene


  A segment of DNA information that is used to make chromosomes. When an allele is dominant it is expressed in the phenotype over a recessive allele

  
• Recessive gene


  A gene that can be masked by a dominant gene
• Incomplete Dominance


  Situation in which one allele is not completely dominant over another
• Codominance


  Situation in which both alleles of a gene contribute to the phenotype of the organism
• Multiple Alleles


  Three or more alleles of the same gene
• Polygenic Traits


  Trait controlled by two or more genes
• Genome


  The entire set of genes in chromosomes
• Locus


  A fixed location on a strand of DNA where a gene or one of its alleles is located
• Inheritance


  The process by which the characteristics of individual are passed to their offspring
• Sex Determination


  The sex of an organism is determined by a special sex chromosome
• Three categories of Traits

  • Morphological Traits
  • Physiological Traits
  • Behavioral Traits
• Four Levels of Biological Organization

  • Molecular Level
  • Cellular Level
  • Organism Level
  • Population Level
• Gregor Johann Mendel

  • Father of Modern Genetics
  • Grew up on a farm in Hyncice (formerly Heinzendrof) in Northern Moravia, which was then a part of Austria, and now part of the Czech Republic
  • As young boy he worked with his father grafting trees to improve the family orchard
  • Accepted into the Augustinian monastery of St. Thomas, completed his studies for priesthood, and was ordained in 1847
  • Work as substitute teacher, Mendel enrolled in University of Vienne to expand his knowledge in the area of Mathematics and Physics
  • In 1856, Mendel began his historic studies on pea plants for 8 years, he grew and crossed thousands of pea plants on a small 23 by 115-foot plot
  • He published his work, entitled experiments on Plant hybrids, in 1866
  • This paper was largely ignored by scientist at the time, possibly because of the title, which give indication of its contents
  • Another reason his work went unrecognized could be tied to a lack of understanding of chromosomes and their transmission
  • Prior to his death in 1884, Mendel reflected, "My scientific work has brought me a great deal of satisfaction and I am convinced that it will be appreciated before long by the whole world"
• Hybridization experiment


  When two distinct individuals with different characteristics are bred or crossed, their offspring is called HYBRIDS
• Mendel chose the garden PEA, (Pisum sativum), because they are ideal for heredity as they are easy to grow/develop, easy to breed, and they also have many traits that take one of two easily distinguished forms that were illustrated in several generations
• The first experiment dealt with a single trait with two expressions, short and tall. He set up all the combinations of a possible artificial pollinations, manipulating fertilization to cross the tall with tall/short with short, and tall with short plants
• The last combination is where the plants with one trait variant crossed with plants with the alternate trait to produce a hybrid, which is the offspring that inherited the different gene variants from both parents
• The term gamete is used to describe haploid reproductive cells that can unite to form a zygote
• In plants, male gametes (sperm) are produced within pollen grains formed in the anthers