Genetics 4-6

• Cell Division & Genetic Material


  The study of how genetic information is passed from one generation of organisms or cells to the next generation
• Genetics


  The study of how genetic information is passed from one generation of organisms or cells to the next generation
• All living things are composed of one or more cells
• Cells are the smallest units of living organisms
• New cells come only from pre-existing cells by cell division
• Inheritable Traits


  Traits are passed on through genetic material in the form of deoxyribonucleic acid (DNA)
• Cell Division


  1. Cell divides

  2. Each new cell receives genetic information from the parent cell
• Cell Cycle


  All somatic cells (body cells of plants and animals) go through the cell cycle
• Purpose of Cell Cycle

  • Growth
  • Repair (tissues/organs)
  • Replace dying or dead cells
• Duration of Cell Cycle

  12 - 24 hrs to years
• Stages of the Cell Cycle

  • Interphase
  • Mitosis
  • Cytokinesis
• Interphase


  Cell carries out its normal functions, grows, and makes copies of its genetic material in preparation for the next stage of the cycle
• Mitosis


  A cell's nucleus and genetic material divide
• Cytokinesis


  Begins near the end of mitosis, involves the division of the cell cytoplasm and creation of a new cell
• Interphase


  • DNA replicated
  • Organelles replicated
  • Cell increases in size
  • DNA exists as uncondensed fibres called chromatin
• Heredity


  The transmission of characteristics from one generation to the next
• Prophase


  • Packages DNA into chromosomes
  • Each chromosome exists as two copies of one chromosome
  • Nuclear membrane breaks down & the nucleolus disappears
  • Spindle fibres are formed from the centrosomes
• Genetics


  The science which deals with the study of heredity
• Inheritance Patterns


  The predictable patterns seen in the transmission of traits from one generation to the next
• Gregor Mendel (1822-1884) was an Augustinian monk in Austria who used garden pea plants to explain the inheritance of characteristics
• Gregor Mendel's pea plant experiments

  • Examined seven different pea traits
  • Each trait had only two possible variations (alleles) e.g. yellow or green seed colour
• Metaphase


  • Chromosomes line up at the center of the cell
  • Spindle fibers attach from daughter cells to chromosomes at the centromere
• Alleles


  Different forms of the same gene
• Anaphase


  • Centromeres split apart
  • Spindle fibers pull chromosomes apart
  • The separated sister chromatids are now referred to as chromosomes
  • Spindle fibres shorten, pulling the chromosomes to opposite poles
• Why the common pea plant was suitable for Mendel's genetic experiments

  • Commercially available throughout Europe
  • Easy to grow & matured quickly
  • Has several characteristics that express themselves as pairs of contrasting traits
  • Is a self-pollinating plant (allows one to control which individuals are crossed)
• How Mendel performed his pea breeding experiments

  1. Choosing a female parent plant

  2. Choosing a male parent

  3. Collecting pollen from the stamens and dusting onto the female parent stigma
• Telophase


  • DNA spreads out (unwinds into chromatin)
  • 2 nuclei, nuclear membranes & nuclear envelopes form
  • Cell wall starts to pinch in (cleavage furrow)
• Dominant


  The form of a trait that always appears when an individual has an allele for it
• Cytokinesis


  Cell wall continues to pinch in (cleavage furrow) until 2 new daughter cells are formed
• Recessive


  The form of a trait that only appears when an individual has two alleles for it
• In plant cells, a cell plate forms separating the two daughter nuclei
• Monohybrid


  A cross of two individuals that differ by one trait
• Homozygous


  An individual who has two identical alleles of a gene
• DNA Structure


  DNA consists of two molecules that are arranged into a ladder-like spiral shape structure called a double helix
• Heterozygous


  An individual who has two different alleles of a gene
• Nucleotides


  A molecule of DNA is made up of millions of tiny subunits called Nucleotides
• Genotype


  The combination of alleles for any given trait
• Phenotype


  The physical & physiological traits of an organism (can be seen/observed)
• Mendel was the first to propose the Principle of Dominance, the Law of Segregation, and the Law of Independent Assortment
• Components of a Nucleotide

  • Phosphate group
  • Pentose sugar
  • Nitrogenous base