Topic2 Cell

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Topic2 Cell

  1. 1. Copyright © FSFS Sept 2005 Open University Malaysia TOPIC 2: THE NUCLEUS, CHROMOSOME AND DNA Azizah Mohd. Asi SBBI4103 Cell Biology and Cellular Biochemistry September 2005
  2. 2. <ul><li>Nucleus </li></ul><ul><li>Chromosome </li></ul><ul><li>DNA structure and function </li></ul><ul><ul><li>Gene regulation and expression </li></ul></ul><ul><li>DNA replication </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  3. 3. NUCLEUS <ul><li>What are the importance of nucleus? </li></ul><ul><ul><li>genetic information carrier </li></ul></ul><ul><ul><li>DNA replication </li></ul></ul><ul><ul><li>RNA synthesis </li></ul></ul><ul><li>What are the functions of nucleus? </li></ul><ul><li>What are the structures of nucleus? </li></ul><ul><ul><li>nuclear envelope </li></ul></ul><ul><ul><li>chromatin </li></ul></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  4. 4. CHROMOSOME <ul><li>What is chromosome? </li></ul><ul><li>A threadlike structure found in the nucleus. </li></ul><ul><li>Contains both DNA and protein. </li></ul><ul><li>Composed of chromatin or DNA-protein complex. </li></ul><ul><li>Carry the genes in a linear sequence. </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  5. 5. CHROMOSOME (2) Copyright © FSFS Sept 2005 Open University Malaysia Prokaryotic chromosome Eukaryotic chromosome <ul><li>Can be found in bacterial cells. </li></ul><ul><li>Can be found in the nucleus of eukaryotic cells – protists, fungi, animals and plants. </li></ul><ul><li>Circular double-stranded DNA molecule packaged into the region called nucleoid. Does not contain chromatin. </li></ul><ul><li>Tightly packaged in the chromosome within the nucleus. Chromatin functions the same to the nucleus as cytoplasm to the entire cell. </li></ul><ul><li>In E.coli DNA molecule contains 4.6 million base pairs. </li></ul><ul><li>In human, the length of the chromosomes vary between 1.6 cm to 8.4 cm (about 1000 times more DNA than E.coli ). </li></ul>
  6. 6. CHROMOSOME (3) <ul><li>The structure of chromosome: </li></ul><ul><li>Centromere </li></ul><ul><li>Telomere </li></ul><ul><li>Chromatin </li></ul><ul><li>30 nm fibre form </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  7. 7. CHROMOSOME (4) <ul><li>The structure of eukaryotic chromosome </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  8. 8. CHROMOSOME (4) <ul><li>The structure of chromatin </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  9. 9. Copyright © FSFS Sept 2005 Open University Malaysia
  10. 10. DNA STRUCTURE AND FUNCTION <ul><li>DNA is made up of four different nucleotides: </li></ul><ul><ul><li>cytosine </li></ul></ul><ul><ul><li>adenine </li></ul></ul><ul><ul><li>thyamine </li></ul></ul><ul><ul><li>guanine </li></ul></ul><ul><ul><li>(Which are purines and which are pyrimidines?) </li></ul></ul><ul><li>Each nucleotide is made up of three elements : </li></ul><ul><ul><li>phosphate </li></ul></ul><ul><ul><li>deoxyribose sugar </li></ul></ul><ul><ul><li>nitrogenous base </li></ul></ul><ul><li>A phosphodiester bond links these nucleotides. </li></ul><ul><li>(see figures 2.5, 2.6 and 2.7 on pages 22-23) </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  11. 11. DNA STRUCTURE AND FUNCTION (2) <ul><li>DNA structure: </li></ul><ul><li>Two complementary anti-parallel chains of DNA wound around each other following a helical path, resulting in a right-handed double helix . </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  12. 12. DNA STRUCTURE AND FUNCTION (3) Copyright © FSFS Sept 2005 Open University Malaysia
  13. 13. DNA STRUCTURE AND FUNCTION (4) <ul><li>BASE PAIRING: </li></ul><ul><li>Purine – Pyrimidine </li></ul><ul><li>T – A </li></ul><ul><li>C – G </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  14. 14. DNA STRUCTURE AND FUNCTION (5) <ul><li>The Central Dogma </li></ul><ul><li>DNA  RNA  PROTEIN </li></ul><ul><li> TRANSCRIPTION TRANSLATION </li></ul><ul><ul><li>(see Figure 2.12 on page 28 ) </li></ul></ul><ul><ul><li>DNA codes for the production of RNA </li></ul></ul><ul><ul><li>RNA codes for the production of protein </li></ul></ul><ul><ul><li>Protein DOES NOT code for the production of protein, RNA or DNA </li></ul></ul><ul><li>(Is there exception for these rules, ie. reverse transcribe?) </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  15. 15. DNA STRUCTURE AND FUNCTION (6) <ul><li>Gene regulation and expression </li></ul><ul><ul><li>Transcription </li></ul></ul><ul><ul><li>Translation </li></ul></ul><ul><ul><li>Eukaryotic gene expression </li></ul></ul><ul><ul><li>Prokaryotic gene expression </li></ul></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  16. 16. GENE EXPRESSION Copyright © FSFS Sept 2005 Open University Malaysia Eukaryotic Prokaryotic <ul><li>Transcription – in the nucleus; translation – in the cytoplasm; mRNA longer-lived </li></ul><ul><li>Transcription and translation – in the cytoplasm </li></ul><ul><li>mRNAs encode only one protein - monocistronic </li></ul><ul><li>mRNA may contain regions coding for one or more proteins, or polycistronic </li></ul><ul><li>Forms pre-mRNAs that would undergo splicing, capping and polyadenylation, to form mature mRNA </li></ul>
  17. 17. GENE EXPRESSION (2) <ul><li>DO YOU KNOW, WHAT IS: </li></ul><ul><li>a promoter ? </li></ul><ul><li>a terminator ? </li></ul><ul><li>an intron ? </li></ul><ul><li>an exon ? </li></ul><ul><li>RNA Pol II ? </li></ul><ul><li>snRNP ? </li></ul><ul><li>During eukaryotic gene expression the pre-mRNA would undergo splicing and capping to form mature mRNA that will be transported to the cytoplasm. Why is this so? </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  18. 18. DNA REPLICATION <ul><li>What is DNA replication? </li></ul><ul><li>How do DNAs replicate? </li></ul><ul><li>When do DNAs replicate? </li></ul><ul><li>What is a replicon ? </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  19. 19. SUMMARY <ul><li>Eukaryotic nucleus carries the genetic information of the cell in multiple chromosomes, each containing a single DNA molecule. </li></ul><ul><li>Eukaryotic cells have true nucleus (membrane-bounded) while prokaryotic cells have nuclear material (a circular double-stranded DNA molecule) concentrated in a region called nucleoid (does not have chromatin). </li></ul><ul><li>Chromosomes in eukaryotic cells are composed of chromatin (DNA-protein complex). </li></ul><ul><li>DNA is made up of nucleotide units which composed of phosphate, deoxyribose sugar and nitrogenous base. </li></ul><ul><li>Two complementary, anti-parallel DNA strands coiled up in a helical path, in a double-helix structure. </li></ul><ul><li>In protein synthesis, DNA makes RNA which makes protein. This happens via the process of transcription and translation, respectively. </li></ul><ul><li>DNA replication involves the process where two DNA parental strands separate to direct enzyme-catalysed synthesis of new complementary daughter strands following the normal base-pairing A-T, G-C rule. </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  20. 20. ON-LINE DISCUSSION <ul><li>Discuss the distinctive features of eukaryotic chromosome. </li></ul>Copyright © FSFS Sept 2005 Open University Malaysia
  21. 21. Copyright © FSFS Sept 2005 Open University Malaysia Terima Kasih

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