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  1. 1. Modern Genetics
  2. 2. Importance of DNA
  3. 3. <ul><li>By the beginning of the 1900’s, it was known that the chromosomes carry the genetic or hereditary information. </li></ul><ul><li>Heredity is controlled mostly by genes and to some degree by the environment. </li></ul><ul><li>For example, all plants can make chlorophyll (which makes them green). There is a gene that gives them this ability. If a seed is grown in the dark, the leaves will come up white, not green (environment played a role.) </li></ul>
  4. 4. <ul><li>The hereditary material is DNA (deoxyribonucleic acid). </li></ul><ul><ul><li>DNA makes up genes </li></ul></ul><ul><ul><li>Genes make up chromosomes </li></ul></ul><ul><li>Another example: Identical twins have identical genes but may have some differences if raised in different places or eat different foods etc. </li></ul>
  5. 5. <ul><li>DNA is a nucleotide made of 3 parts: </li></ul>P S Base <ul><ul><li>1. A phosphate group </li></ul></ul><ul><ul><li>2. A deoxyribose molecule, which is a sugar molecule with 5 carbon atoms. </li></ul></ul><ul><ul><li>3. A nitrogenous base, which may be one of four kinds: </li></ul></ul><ul><ul><ul><li>Adenine </li></ul></ul></ul><ul><ul><ul><li>Thymine </li></ul></ul></ul><ul><ul><ul><li>Guanine </li></ul></ul></ul><ul><ul><ul><li>Cytosine </li></ul></ul></ul>nucleotide
  6. 6. DNA molecules
  7. 7. Watson-Crick Model of DNA <ul><li>James Watson and Francis Crick developed a model of DNA. </li></ul><ul><li>According to this model, the DNA consists of two chains of nucleotides in a ladder-like structure. </li></ul><ul><li>The sides of the ladder are made of alternating phosphate and deoxyribose (sugar). </li></ul><ul><li>A nitrogenous base is attached to each sugar molecule. </li></ul><ul><li>The steps of the ladder are held together by weak hydrogen bonds between the bases. </li></ul>
  8. 8. Watson & Crick 2 mins.
  9. 11. <ul><li>Only two base pair combinations can form in the DNA molecule </li></ul><ul><ul><li>Adenine (A) with Thymine (T) </li></ul></ul><ul><ul><li>Guanine (G) with Cytosine (C) </li></ul></ul><ul><ul><li>So A-T, T-A, C-G, and G-C are the only possible base pair rungs of the DNA ladder. </li></ul></ul>
  10. 12. Question… <ul><li>If one strand of the DNA molecule has the base sequence below, draw the other strand. </li></ul><ul><ul><li>A - </li></ul></ul><ul><ul><li>T - </li></ul></ul><ul><ul><li>G - </li></ul></ul><ul><ul><li>C - </li></ul></ul>C A T G
  11. 13. Parts of DNA 4 min.
  12. 14. <ul><li>The DNA ladder is twisted to form a structure called a double helix (like a spiral staircase). </li></ul><ul><li>Watson and Crick discovered the structure of the double helix. They also discovered how DNA replicates (copies itself) during mitosis and meiosis. </li></ul>DOUBLE HELIX
  13. 15. Review of DNA 1 min.
  14. 18. Watson and Crick found that DNA: <ul><li>STEP 1: DNA unzips itself at the base pairs along the weak hydrogen bonds. </li></ul><ul><li>STEP 3: The new double stranded molecules that form are identical to the original molecule. </li></ul><ul><li>STEP 2: Free nucleotides that are present in the nucleus attach themselves by new hydrogen bonds to the free bases. </li></ul>
  15. 21. Replication of DNA 1.15
  16. 22. G T G A C C
  17. 23. DNA Replication A G C T C T C A A A C T C G T G T G A G T A C T T T T G G G C A A A A A A C C C C G T T
  18. 25. Gene Control
  19. 26. Gene Control - The Genetic Code <ul><li>A gene is a particular section of a DNA molecule. </li></ul><ul><li>It is believed that the base-pair sequence (order) of the gene controls cellular activity by specifying a protein. </li></ul><ul><li>The nitrogenous bases are like letters in an alphabet. The DNA molecule is a sequence of bases that spell out words in the DNA code. The code is eventually converted into an amino acid sequence to make the appropriate proteins needed by the organism. </li></ul>
  20. 27. <ul><li>The code is a triplet code. </li></ul><ul><li>Every word has 3 letters in it. </li></ul><ul><li>Each 3 letter sequence of bases on DNA template will lead to a complementary 3 letter sequence called a codon. </li></ul><ul><ul><li>Ex: CAG, GGC, ACG </li></ul></ul><ul><li>Every codon (3 bases) will code for one amino acid that will be put in place to make a protein. </li></ul>
  21. 28. <ul><li>DNA (with its important code) stays inside the nucleus. </li></ul><ul><ul><li>Proteins are made outside the nucleus on organelles called ribosomes. </li></ul></ul><ul><li>The DNA needs help to get the information outside the nucleus to make the proteins it codes for. </li></ul><ul><li>One strand of DNA will act as the template for a different nucleic acid that can leave the nucleus. </li></ul>
  22. 30. <ul><li>RNA = ribonucleic acid. </li></ul><ul><li>This form of nucleic acid helps DNA perform the synthesis of proteins. </li></ul><ul><li>RNA is different from DNA because: </li></ul><ul><ul><li>It is single stranded. </li></ul></ul><ul><ul><li>It has ribose as its sugar. </li></ul></ul><ul><ul><li>The base thymine (T) is replaced by uracil (U). </li></ul></ul>
  23. 31. The drawing is RNA because it has U as a base And not T. You can also tell that it is RNA because it is single- stranded.
  24. 32. There are 3 types of RNA… <ul><li>1. Messenger RNA (mRNA) </li></ul><ul><ul><li>This is the RNA copy of the DNA </li></ul></ul><ul><li>2. Transfer RNA (tRNA) </li></ul><ul><ul><li>This transfers the amino acids onto the mRNA. </li></ul></ul><ul><li>3. Ribosomal RNA (rRNA) </li></ul><ul><ul><li>This is where the construction of the protein takes place. </li></ul></ul>
  25. 35. <ul><li>Each group of 3 nucleotides (bases) is called a codon. </li></ul><ul><ul><li>Examples: AUU, GCC, UCG </li></ul></ul><ul><li>Each amino acid is coded for by a particular codon (3 nucleotides). </li></ul><ul><li>Each transfer RNA carries an anticodon of three bases that matches the codon. </li></ul><ul><li>This ensures that the right amino acids go into the protein. </li></ul>
  26. 38. QUESTION: <ul><li>If the DNA code is ACT AGG CCA….. </li></ul>The mRNA will be: The tRNA will be: UGA, UCC, GGU (codons) ACU, AGG, CCA (anticodons) The transfer RNA will bring the correct 3 Amino acids to the ribosome.
  27. 43. <ul><li>Transcription </li></ul><ul><ul><li>Production of mRNA from DNA to leave nucleus with code. </li></ul></ul><ul><li>Translation </li></ul><ul><ul><li>The production of proteins (amino acid chain) from a nucleotide chain. </li></ul></ul>
  28. 44. Protein Synthesis 3 min.
  29. 47. Modern DNA Technology 1. Cloning 2. Genetic Engineering 3. Gene Therapy 4. DNA Fingerprinting
  30. 48. <ul><ul><li>Identical copies of an organism without fertilization. </li></ul></ul><ul><ul><li>Egg cell  remove monoploid nucleus  add diploid nucleus from a mammary cell or any other cell of an adult organism  egg cell with new nucleus is transplanted into uterus of another organism  new individual produced is identical to original. </li></ul></ul><ul><ul><li>Example: Dolly (sheep) cloned in 1997 by Dr. Ian Wilmut </li></ul></ul>1. Animal Cloning
  31. 52. <ul><li>2. Genetic Engineering </li></ul><ul><ul><li>RECOMBINANT DNA = DNA combined from 2 different organisms to produce characteristics not found in nature. </li></ul></ul><ul><ul><li>Uses restriction enzymes to split DNA. </li></ul></ul><ul><ul><li>The sticky ends at the cut can be touched to another DNA piece and adhere to it. </li></ul></ul>
  32. 53. Example of Recombinant DNA: <ul><li>E. Coli </li></ul><ul><ul><li>E. Coli is a bacterium with a large DNA molecule and 2 smaller DNA rings called plasmids . </li></ul></ul><ul><ul><li>A plasmid was spliced and the gene that codes for insulin was transplanted into bacteria. </li></ul></ul><ul><ul><li>Bacteria reproduce often so it made a lot of insulin very fast. </li></ul></ul><ul><ul><li>This is also being done with growth hormone and other needed substances. </li></ul></ul>
  33. 58. Genetic Engineering 4 mins.
  34. 59. __________________________________________________________________________________________________________________________________ Molecule A was made using Recombinant DNA. A human gene for insulin was Combined with the DNA of a Bacterial cell.
  35. 60. <ul><li>-Gene therapy = a technique in which scientists hope to add “normal” copies of genes into cells of people who do not inherit the normal genes for given substances and end up with diseases. </li></ul>3. Gene Therapy
  36. 62. <ul><li>4. DNA Fingerprinting </li></ul><ul><ul><li>Extract a person’s DNA </li></ul></ul><ul><ul><li>Use restriction enzymes to cut them into fragments </li></ul></ul><ul><ul><li>Pieces will end up in different sizes from different people. </li></ul></ul><ul><ul><li>DNA fragments are separated by electrophoresis. Lines formed by each person’s individual DNA will be unique. </li></ul></ul>
  37. 71. <ul><li>A gene mutation is a change in the chemical structure of the genetic material, DNA. </li></ul><ul><li>Most gene mutations are recessive, like albinism (lack of skin pigments). </li></ul><ul><li>Mutations are usually disadvantageous (not good) to the individuals in their normal environment and some may be lethal (can kill). </li></ul><ul><li>Mutations on the other hand, are the basis for evolution. Sometimes mutations are good! </li></ul>
  38. 72. <ul><li>Agents that cause mutations… </li></ul><ul><li>Any substance that causes a mutation is called a mutagenic agent. </li></ul><ul><li>Examples of mutagenic agents…. </li></ul><ul><ul><li>X-rays </li></ul></ul><ul><ul><li>ultraviolet rays </li></ul></ul><ul><ul><li>cosmic rays </li></ul></ul><ul><ul><li>radiation </li></ul></ul><ul><ul><li>formaldehyde </li></ul></ul><ul><ul><li>benzene </li></ul></ul><ul><ul><li>asbestos </li></ul></ul>
  39. 74. The Genetic Code
  40. 75. Genetic Counseling 9 minutes