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  1. 1. History• Frederick Griffith (1928) – experimented with pneumonia – ability to cause disease was inherited by the transformed bacteria’s offspring, the transforming factor might be a gene• Oswald Avery (et al.) (1944) – nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next (genes are composed of DNA)
  2. 2. Cont.• Hershey-Chase (1952) – genetic material of the bacteriophage was DNA, not protein• Watson-Crick – develop the double-helix model of the structure of DNA• Gilbert-Maxam-Sanger (1977)-develop methods to read the DNA sequence• Human Genome Project (2000) – sequence all human DNA
  3. 3. Function of DNA• 1. genes have to carry information from one generation to the next• 2. put information to work by determining the heritable characteristic of organisms• 3. genes have to be easily copied
  4. 4. Components• DNA – long molecule made up of units celled nucleotides• Nucleotides: – 5-carbon sugar – Phosphate group – Nitrogenous base
  5. 5. Cont.• Purines:• Adenine and guanine• Pyrimidines:• Cytosine and thymine• Form chains in A=T and G=C (Chargaff’s rules)• Base pairing – hydrogen bonds form between certain bases
  6. 6. Cont.• Chromatin – DNA and a protein (histones) called nucleosomes• Nucleosomes can fold DNA into tiny space
  7. 7. Replication• Each strand of DNA in the double helix has the exact information needed to copy itself• Produces two new complementary strands following the rules of base pairing• Each strand of the double helix of DNA serves as a template for the new strand
  8. 8. Cont.• Replication – duplicates its DNA (replication forks)• Enzymes “unzip” by breaking the hydrogen bond• DNA polymerase is the enzyme used in replication and “proofreads” the DNA to maximize the perfect copy of DNA
  9. 9. RNA and Protein Synthesis• RNA –long chain of nucleotides of sugar, phosphate and base• Differences: – Ribose (sugar) – Generally single-stranded – Contains uracil in place of thymine
  10. 10. Cont.• Three main types of RNA: mRNA, rRNA, and tRNA• mRNA: carry copies of instructions for assembling amino acids into proteins; serve as a “messenger” for DNA to rest of the cell• rRNA: proteins are assembled on ribosomes
  11. 11. Cont.• tRNA: transfers each amino acid to the ribosome as it is specified by coded messages in mRNA• Transcription: RNA polymerase binds to DNA and separates the DNA strand, RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA
  12. 12. Cont.• RNA polymerase enzyme will only bind to DNA regions where promoters are present, which have specific base sequences• Introns are not involved in coding proteins, exons are the DNA sequences that code for proteins and are “expressed” in the synthesis of proteins
  13. 13. Cont.• Introns are removed from the final RNA molecule and the exons are spliced together to from the mRNA• Proteins form from long chains of amino acids called polypeptides – containing and or all of the 20 different amino acids• mRNA’s “language” of instructions is called the genetic code
  14. 14. Cont.• Bases on RNA – A, U, C, G read 3 letters at a time, each coded “word” is called a codon and will represent a specific amino acid or stop codons• Translation - decoding or reading of codons takes place in ribosomes, and uses information from mRNA to produce proteins
  15. 15. Steps in RNA• 1. mRNA transcribes from DNA in nucleus and released into cytoplasm• 2. mRNA in cytoplasm attaches to ribosome and each codon of mRNA moves through the ribosome and specific amino acid is transferred to polypeptide chain ---tRNA has 3 unpaired bases called anticodon
  16. 16. Mutations• Mutations – mistakes (harmful/beneficial)• Changes in genetic material• Point mutation happens at a single point in a base and includes: substitution, deletion, and insertion and are called frame shift mutations• Causes can be dramatic as code has “shifted” from that point on
  17. 17. Cont• Chromosomal mutations• Deletion – loss of all or part of chromosome• Duplication – extra copy is produced• Inversion – reverses the direction of parts of chromosomes• Translocation – chromosome breaks off and attached to another
  18. 18. Cont.• Harmful – cause many genetic diseases (Down Syndrome, Turner’s syndrome, Fragile X syndrome and cancers)• Beneficial – large crops, allows for variations in species
  19. 19. Progeria
  20. 20. 22q11 deletions
  21. 21. Wolf-Hirschhorn
  22. 22. Neurofibromatosis
  23. 23. Proetus Syndrome
  24. 24. Regulation• Operon – group of genes that operate together• Eukaryotic genes are controlled individually and have regulatory sequences that are complex• Differentiation – specialized structure and function• Hox genes – control cells and tissues