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Interest Grabber

Inside the Nucleus. Interest Grabber. Genes are made of DNA DNA is composed of individual units called nucleotides Three of these units form a code (codon). The order, or sequence, of the code determine the meaning of the message.  DNA Nucleotides. Purines. Pyrimidines. Adenine. Guanine.

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Interest Grabber

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  1. Inside the Nucleus Interest Grabber

  2. Genes are made of DNA • DNA is composed of individual units called nucleotides • Three of these units form a code (codon). • The order, or sequence, of the code determine the meaning of the message

  3.  DNA Nucleotides Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose

  4. Structure of DNA DNA Structure Link Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

  5. Chargaff’s Rules

  6. X-ray diffraction • Rosalind Franklin • X-rayed DNA from a calf thymus gland but had no idea what it was • James Watson saw this x-ray & interpreted DNA as a double helix

  7. James Watson & Francis Crick

  8. Chromosome Structure of Eukaryotes Nucleosome Chromosome DNA double helix Coils Supercoils Histones Chromatin

  9. Chromosome Structure • 1 nanometer = 0.001 micrometer • 1 micrometer = 0.001 millimeter • So • 1 nm = 0.000001 mm

  10. DNA Replication Original strand New strand DNA polymerase Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand

  11. Replication Link

  12. Replication – Making New DNA • Helicase separates two strands of DNA by breaking hydrogen bonds • Primase starts replication • DNA polymerase “polymerizes” the individual nucleotides & proof-reads the new DNA

  13. Now that new cells have been made, new proteins will be needed. • HOW ARE PROTEINS MADE? • We first need to look at something called RNA

  14. Messenger RNA Ribosomal RNA Transfer RNA Bringamino acids toribosome Combine with proteins tRNA mRNA Carry instructions rRNA DNA Ribosome Ribosomes RNA Concept Map RNA can be also called which functions to also called which functions to also called which functions to from to to make up

  15. How is RNA different than DNA? • RNA • Contains ribose instead of deoxyribose • Single stranded • Nucleotide uracil replaces thymine

  16. Transcription • Messenger RNA = mRNA • Carries amino acid sequence to the ribosome • Transfer RNA = tRNA • Carries amino acid to the codon on mRNA • Codon = 3 nucleotide bases on mRNA which “code” for an amino acid • Anticodon = 3 nucleotide bases on tRNA which match up with the codon

  17. Codon

  18. Transcription – Making a Copy of the DNA Transcription Link Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA

  19. Transcription – Making a Copy of the DNA • RNA polymerase separates the DNA strands at a promoter region on the DNA • mRNA adds nucleotides in sequence • RNA polymerase falls off the DNA at a terminator sequence on the DNA

  20. RNA Editing • Introns - Intervening sequence = Junk DNA • Exons – Expressed sequence • Introns are cut out of the mRNA • Exons are held together by a cap and a poly A tail

  21. The Genetic Code - Amino Acid Sequence 4 x 4 x 4 = 64Possible Codons for 20 amino acids AUG = Start Codon Begins transcription AAU, GAU, AGU Stop Codons which end transcription

  22. Translation – On the Ribosome

  23.  Translation (continued) Translation Link

  24. Determining the Sequence of a Gene • DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.

  25. Gene Mutations: Substitution, Insertion, & Deletion Deletion Insertion Substitution Frameshift Mutation

  26. Chromosomal Mutations Deletion Duplication Inversion Translocation

  27. Typical Gene Structure Promoter(RNA polymerase binding site) Regulatory sites DNA strand Start transcription Stop transcription

  28. Gene Regulation • Operon – A group of genes that operate together • Lac Operon = operon expressed in E. coli to use the sugar lactose • Operator – region where repressor protein binds • Promoter – region that signals beginning of operon

  29. lac Operon

  30. lac Operon

  31. lac Operon

  32. lac Operon

  33. Tying it altogether - the lac Operon Gene E. Coli bacteria can synthesize lactase, which is an enzyme that breaks down lactose. Lactase is only synthesized in the presence of lactose. If there is no lactose in the environment, the gene is repressed. E. Coli has three genes that code for lactase. It also has an operator and a promotor. Without lactose, the lac repressor binds to the operator site. With lactose, the repressor is removed Once repressor is removed, RNA polymerase binds to the promoter RNA is transcribed, which is then translated, and becomes the lactase enzyme. Gene Regulation

  34. Cell Growth & Reproduction • Why replicate the DNA? • To make new cells • To replace old worn out cells • To replace damaged cells

  35. Cell Size Limitations • Why are cells so small? • Cell size Limitations • - Diffusion (The bigger the cell the slower the diffusion • - DNA (Large cells need more DNA to make more proteins) • - Surface area to volume ratio

  36. Cell Size Limitations Surface Area-to-volume Ratio

  37. Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume

  38. Chromosome Structure • Sister chromatids • Centromere – attaches chromatids • 46 Chromosomes in humans

  39. M phase (Mitosis) Interphase G1 phase S phase G2 phase Prophase Metaphase Anaphase Telophase Concept Map – Cell Cycle Cell Cycle includes is divided into is divided into

  40. The Cell Cycle G1 phase M phase S phase G2 phase

  41. Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Figure 10–5 Mitosis and Cytokinesis Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

  42. Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

  43. Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

  44.  Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

  45. Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

  46. Mitosis and Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

  47. Interphase • Events of Interphase • Cell grows • DNA replicates • Centriole replication • NOT PART OF MITOSIS

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