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Molecular Biology: Nucleotides, DNA Replication & Cell Cycle Control

Explore key concepts in molecular biology including nucleotide structures, DNA replication, and cell cycle regulation. Learn about nucleic acids, replication proteins, genetic mutations, and signaling pathways. Dive into the world of biology at a molecular level.

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Molecular Biology: Nucleotides, DNA Replication & Cell Cycle Control

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  1. Selected topics in molecular biology Review session Nov. 26, 2007

  2. All nucleotides have a common structure

  3. There are five principal bases in nucleic acids Inosine is carbonylated adenosine A, G, T, C are present in DNA A, G, U, C are present in RNA

  4. UMP

  5. Conversion of ribo-to-deoxyribonucleotides • 1) Ribonucleotide reductase catalyzes the • synthesis of deoxyribonucleotides • Inhibited by hydroxyurea, which is used as anti-cancer drug 2) Thymidylate synthase catalyzes the methylation of dUTP UMP

  6. Anti-cancer drugs specifically block dTMP production Folic acid

  7. Defects in the purine salvage pathway cause human diseases Salvage Pathway Activated ribose (PRPP) + base Blocked by HGPRT deficiency (Gout, Lesh-Nyhan) Nucleotides PRPP De Novo Pathway Activated ribose (PRPP) + amino acids + ATP + CO2 +………. Nucleotides

  8. DNA can undergo reversible strand separation

  9. Replication protein A Replication factor C The eukaryotic replication fork

  10. Inhibited by rifamycins (e.g., Rifampicin)

  11. The base pair in the 3rd codon position can “wobble”

  12. frameshift mutations

  13. Exchange of genetic material during meiosis Recombination=crossover + exchange of DNA between two DNA double strands

  14. Organization and rearrangement of heavy-chain DNA V=variable D=diversity J=joining C=constant VDJ recombination allows for antibody diversity

  15. Different classes of immunoglobulin (isotypes) fulfill different tasks 1st line of defense major class major class membrane- unknown against In serum in external bound parasites, secretions allergies

  16. Cell Cycle Control

  17. Multiple cdks and cyclins regulate passage of mammalian cells through the cell cycle Cdc2/Cdk1-cyclin B Cdc2/Cdk1-cyclin A Cdk4-cyclin D Cdk6-cyclin D Restriction point is analogous to START Cdk2-cyclin A Cdk2-cyclin E

  18. good genes bad genes proto-oncogenes oncogenes are required for promote uncontolled normal growth growth gain-of-function mutation (can be point mutation, insertion or deletion) tumor suppressors inactive tumor suppressor loss-of-function mutation Besides mutations in proto-oncogene/tumor suppressor coding regions, mutations in gene regulatory elements (promoter) can deregulate the expression pattern

  19. Membrane receptors and signal transduction cascades

  20. Cell-surface receptors belong to different classes

  21. G protein-coupled receptors contain 7 transmembrane alpha-helices

  22. Acetylcholine receptor in the heart muscle opens K+ channels frequency of heart contractions goes down

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