Introduction to cytology


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  • DNA is a double helix in which two strands are wound around each other. Each strand is made up of a chain of nucleotides. The two strands are held together by hydrogen bonds between adenine and thymine and between guanine and cytosine.
  • Identify 5 prime (exposed phosphate) and 3 prime (no exposed phosphate)
  • Eukaryotic chromosomes contain DNA wrapped around proteins called histones. The strands of nucleosomes are tightly coiled and supercoiled to form chromosomes.
  • Introduction to cytology

    1. 1. Objectives: 1. What is Cytology? 2. Explain how prokaryotic & eukaryotic cells differ. 3. What is DNA? 4. Identify the parts and function of the Nucleus.
    2. 2.  It is the study of the structure and function of cells.  The cell is the basic structural and functional unit of life so therefore cytology is the fundamental most important topic in all of biology.
    3. 3.  Cytoplasm : area of space outside the nucleus; contains the organelles & cytosol.  Organelles : are tiny structures in the cytoplasm which perform various jobs for the cell.  Cytosol : is the fluid part of the cytoplasm.
    4. 4.  They lack a nuclear membrane as well any other membrane covered organelles in their cytoplasm.  Considered to be “Primitive Cells”  Example : Bacteria & Blue- Green Algae
    5. 5.  They possess a nuclear membrane as well as membrane bound organelles in their cytoplasm.  Example : Plant & Animal Cells
    6. 6.  is the computer or control center of the cell.  contains the genetic material of life DNA (Deoxyribonucleic acid).  discovered by James Watson, Francis Crick, & Rosalind Franklin (1953).  a DNA molecule consists of nucleotides connected together.
    7. 7. A nucleotide consists of a : 1. Phosphate group 2. Deoxyribose sugar 3. Nitrogen base: 4 types Adenine (A) Thymine (T) Cytosine (C) Guanine (G) DNA consists of two nucleotide chains connected together. A & T always pair up, while C & G do the same.
    8. 8. DNA Double Helix
    9. 9.  Your genetic code is found in groups of 3 rungs in the ladder called DNA triplets AA TT GG TT AA CC 5’ 3’ 5’3’
    10. 10.  Complete the worksheet entitled “ODE to DNA” .
    11. 11.  Long chains of DNA form Chromatin.  Short sections of DNA along a piece of chromatin form Genes. Human genome contains about 30,000 genes!  A gene will either produce or influence a specific trait in the offspring.
    12. 12. Chromatin Chromatin Supercoils Nucleosome DNA double helix Histones Coils
    13. 13.  Nucleolus / Nucleoli (plural) : a dark spherical structure that is the site of ribosome formation.  Ribosomes and other important chemical messages leave the nucleus through the Nuclear Pores. The membrane around the nucleus is called the Nuclear Membrane or Envelope.