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  1. 1. WARM-UP #7
  2. 2. DNA (Deoxyribonucleic Acid)
  3. 3. Genetic material of cells… <ul><li>GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT </li></ul><ul><li>Called NUCLEIC ACIDS </li></ul><ul><li>DNA is made up of repeating molecules called NUCLEOTIDES </li></ul>
  4. 4. DNA Nucleotide O O=P-O O Phosphate Group N Nitrogenous base (A, G, C, or T) CH2 O C 1 C 4 C 3 C 2 5 Sugar (deoxyribose)
  5. 5. A HISTORY OF DNA <ul><li>Discovery of the DNA double helix </li></ul><ul><li>A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928) </li></ul><ul><li>B. Rosalind Franklin - X-ray photo of DNA. </li></ul><ul><li>(1952) </li></ul><ul><li>C. Watson and Crick - described the DNA molecule from Franklin’s X-ray. </li></ul><ul><li>(1953) </li></ul>SEE p. 292-293
  6. 6. Watson & Crick proposed… <ul><li>DNA had specific pairing between the nitrogen bases: </li></ul><ul><li>ADENINE – THYMINE </li></ul><ul><li>CYTOSINE - GUANINE </li></ul><ul><li>DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule” </li></ul>
  7. 7. DNA Double Helix Nitrogenous Base (A,T,G or C) “ Rungs of ladder” “ Legs of ladder” Phosphate & Sugar Backbone
  8. 8. DNA Double Helix P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C T A
  9. 9. Nitrogenous Bases <ul><li>PURINES </li></ul><ul><li>1. Adenine (A) </li></ul><ul><li>2. Guanine (G) </li></ul><ul><li>PYRIMIDINES </li></ul><ul><li>3. Thymine (T) </li></ul><ul><li>4. Cytosine (C) </li></ul>T or C A or G
  10. 10. Chargaff’s Rule <ul><li>Adenine must pair with Thymine </li></ul><ul><li>Guanine must pair with Cytosine </li></ul><ul><li>Their amounts in a given DNA molecule will be about the same . </li></ul>G C T A
  11. 11. BASE-PAIRINGS C G H-bonds T A
  12. 12. Genetic Diversity… <ul><li>Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms. </li></ul>
  13. 13. The Code of Life… <ul><li>The “code” of the chromosome is the SPECIFIC ORDER that bases occur. </li></ul><ul><li>A T C G T A T G C G G… </li></ul>
  14. 14. DNA is wrapped tightly around histones and coiled tightly to form chromosomes See p. 297
  15. 15. DNA Replication <ul><li>DNA must be copied </li></ul><ul><li>The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing: </li></ul><ul><li>A-T, G-C </li></ul><ul><ul><li>Each strand of the original DNA serves as a template for the new strand See p. 298 </li></ul></ul>
  16. 16. DNA Replication <ul><li>Semiconservative Model: </li></ul><ul><li>1. Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand. </li></ul><ul><li>. </li></ul>Parental DNA DNA Template New DNA
  17. 17. <ul><ul><li>1. Why is replication necessary? </li></ul></ul><ul><ul><li>2. When does replication occur? </li></ul></ul><ul><ul><li>3. Describe how replication works. </li></ul></ul><ul><ul><li>Use the complementary rule to </li></ul></ul><ul><ul><li> create the complementary strand: </li></ul></ul>A--- ? G--- ? C--- ? T--- ? A--- ? G--- ? A--- ? G--- ? C--- ? A--- ? G--- ? T--- ? Replication Quiz
  18. 18. <ul><ul><li>1. Why is replication necessary? </li></ul></ul><ul><li>So both new cells will have the correct DNA </li></ul><ul><ul><li>2. When does replication occur? </li></ul></ul><ul><ul><li>During interphase (S phase). </li></ul></ul><ul><ul><li>3. Describe how replication works. </li></ul></ul><ul><ul><li>Enzymes unzip DNA and complementary nucleotides join each original strand. </li></ul></ul><ul><ul><li>4. Use the complementary rule to </li></ul></ul><ul><ul><li> create the complementary strand: </li></ul></ul>A--- T G--- C C--- G T--- A A--- T G--- C A--- T G--- C C--- G A--- T G--- C T--- A Replication Quiz
  19. 19. (1961) Watson & Crick proposed… <ul><li>… DNA controlled cell function by serving as a template for PROTEIN structure. </li></ul><ul><li>3 Nucleotides = a triplet or CODON </li></ul><ul><li>(which code for a specific AMINO ACID) </li></ul><ul><li>See p.303 </li></ul><ul><li>AMINO ACIDS are the building blocks of proteins. </li></ul>
  20. 20. DNA Transcription <ul><li>DNA can “unzip” itself and RNA nucleotides match up to the DNA strand. </li></ul><ul><li>Both DNA & RNA are formed from NUCLEOTIDES and are called NUCLEIC acids. </li></ul>See p.301
  21. 21. DNA Translation <ul><li>The cell uses information from “messenger” RNA to produce proteins </li></ul>See p.304-305 We will discuss details of this on a later date
  22. 22. Transcription/Translation Quiz <ul><li>Why is transcription necessary? </li></ul><ul><li>Describe transcription. </li></ul><ul><li>Why is translation necessary? </li></ul><ul><li>Describe translation. </li></ul><ul><li>What are the main differences between DNA and RNA. </li></ul><ul><li>Using the chart on page 303, identify the amino acids coded for by these codons: </li></ul><ul><li>UGGCAGUGC </li></ul>
  23. 23. <ul><li>1. Why is transcription necessary? </li></ul><ul><li>Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm. </li></ul><ul><li>2. Describe transcription. </li></ul><ul><li>RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA. </li></ul><ul><li>3. Why is translation necessary? </li></ul><ul><li>Translation assures that the right amino acids are joined together by peptides to form the correct protein. </li></ul>
  24. 24. <ul><li>4. Describe translation. </li></ul><ul><li>The cell uses information from MRNA to produce proteins. </li></ul><ul><li>5. What are the main differences between DNA and RNA. </li></ul><ul><li>DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil. </li></ul><ul><li>Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGC </li></ul><ul><li>tryptophan-glutamine-cysteine </li></ul>
  25. 25. AMAZING DNA FACTS… <ul><li>DNA from a single human cell extends in a single thread for almost 2 meters long!!! </li></ul><ul><li>It contains information equal to some 600,000 printed pages of 500 words each!!! </li></ul><ul><li>(a library of about 1,000 books) </li></ul>
  26. 26. LET’S REVIEW DNA… LM p.44 <ul><li>List the conclusions Griffith & Avery, Hershey & Chase drew from their experiments. </li></ul><ul><li>Summarize the relationship between genes & DNA. </li></ul><ul><li>Describe the overall structure of the DNA molecule. </li></ul><ul><li>What are the 4 kinds of bases? </li></ul>