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Unit 3c

Unit 3c. Microbial Genetics. Microbial Genetics. Genetics : the science of heredity Genome : the genetic information in the cell Genomics : the sequencing and molecular characterization of genomes. Gregor Mendel Grew pea plants f rom 1856-1863. Genetics : the science of heredity

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Unit 3c

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  1. Unit 3c Microbial Genetics

  2. Microbial Genetics Genetics: the science of heredity Genome: the genetic information in the cell Genomics: the sequencing and molecular characterization of genomes • Gregor Mendel • Grew pea plants from 1856-1863. • Genetics: the science of heredity • Genome: the genetic information in the cell • Genomics: the sequencing and molecular characterization of genomes

  3. A cell’s genome includes Plasmids • Chromosomes and _________ • Chromosomes are structures containing the DNA

  4. A bacterium has a single circular chromosome consisting of a single circular molecule of DNA

  5. Plasmids (review) • small loops of extrachromosomal DNA in bacteria • often carry genes for virulence, bacteriocins (toxic proteins that kill other bacteria) or drug resistance (codes for enzymes that inactivate certain drugs or toxic substances) • can recombine into new combinations • transmitted from organism to organism

  6. Eukaryotic DNA sites

  7. DNA • Fig. 2.16 Nucleotides

  8. “Genes” • Segments of DNA (except in some viruses, in which they are made of RNA) that code for functional products DNA

  9. each gene could be several thousand or more base pairs long. • E. coli approximately 4,300 genes (4.6 million base pairs • Humans have approximately 20,000 to 25,000 genes. • Based on Human Genome Project

  10. Nucleic Acids • DNA and RNA • DNA: deoxyribonucleic acid • RNA: ribonucleic acid • Messenger RNA (mRNA) • Ribosomal RNA (rRNA) • Transfer RNA (tRNA) • Nucleotides are the structural units of nucleic acids

  11. Nucleotides (Review) • a nucleic acid is a long chain of nucleotides • each nucleotide has 3 parts: • a 5-carbon ________ • ribose in RNA • deoxyribose in DNA • A __________ group • a ___________ base Sugar Phosphate Nitrogenous

  12. One nucleotide

  13. RNA nucleotide with uracil

  14. Nucleic acids • RNA: usually a single chain of nucleotides (may be double in viruses)

  15. DNA: usually a double chain of nucleotides (may be single in viruses) • 2 kinds of base pairs:

  16. Nucleotides Complementary Base Pair • Nucleotide bases bind to each other in a specific manner = complementary base pairing. • Specific purines complementary base pair with specific pyrimidines. Complementary base pairing in DNA

  17. DNA • Double helix of James Watson and Frances Crick

  18. Review of Proteins: • long chains of amino acids: hundreds of amino acids in complex three-dimensional arrangements • there are 20 naturally occurring kinds of amino acids • each amino acid in a protein must be exactly the right kind of amino acid or it will be a different protein

  19. the function of a gene is to determine the sequence of the amino acids to make a specific protein

  20. The genetic code • The set of rules that determine how a nucleotide sequence is converted into the amino acid sequence • along a mRNA, groups of 3 consecutive nucleotides is a codon, the genetic code for one amino acid • e. g. —P—R—P—R—P—R— l l l U A C • 64 possible mRNA codons for 20 amino acids • there can be up to 6 codons that specify the same amino acid • a few codons specify NO amino acid (start or stop codons),signal the end of the protein molecule’s synthesis

  21. The genetic code

  22. An overview of genetic flow ….figure 8.2

  23. 1) DNA replication • reproduction of a molecule • basis of continuity of life • molecule “unzips” along the hydrogen bonds • each half attracts the nucleotides needed to recreate the other half • if successful, both new molecules are identical to the original and to each other

  24. DNA Replication DNA Polymerase– Enzyme that connects each nucleotide together 3’ 5’ DNA Ligase– Enzyme that connects sections of DNA together Okazaki Fragments Lagging Strand Leading Strand 3’ 5’

  25. Figure 8.6

  26. DNA replication precedes cell division

  27. 2) Transcription • = production of RNA by DNA • DNA produces several kinds of RNA • messenger-RNA (m-RNA) carries the genetic code for a protein out from the chromosome to the ribosomes • transfer-RNA (t-RNA) carries individual amino acids to the messenger RNA which puts them in the proper sequence • ribosomal-RNA (r-RNA) links up the amino acids to form a protein

  28. Translation • = protein synthesis, translating the genetic code into a specific protein chain of amino acids

  29. Fig. 8.10 • Simultaneoustranscription andtranslation inbacteria

  30. RNA Polymerase _________________________Connects RNA nucleotides together (like DNA polymerase) Becomes mRNA (messenger RNA) – this has the code for how to build a protein

  31. tRNA – transfer RNA anticodon & amino acid Codon- A section of three nucleotides in a row that code for an amino acid

  32. Polypeptide Chain – all the amino acids who together

  33. Mutations • Can be negative, neutral, or positive! • defined as a change in the base sequence of DNA • can involve one or more nucleotides • the source of new genes (such as virulence or drug resistance) • about one mutation per million replicated genes • causes: • errors in DNA replication • radiation • mutagenic chemicals

  34. The electromagnetic spectrum: effective wave lengths: • a. ultraviolet radiation • damages DNA • optimum wave length: 260 nm • poor penetrating ability

  35. Ames Test uses bacteria as carcinogenindicators (figure 8.22) • Many known mutagens have been found to be carcinogens

  36. Genetic Recombination • The exchange of genes between 2 DNA molecules to form new combinations of genes on a chromosome. • Vertical gene transfer • Genes are passed from an organism to its offspring • Horizontal gene transfer • Between bacteria of the same generation! • Donor cell to recipient cell = recombinant

  37. An overview of genetic flow ….figure 8.2

  38. Bacterial gene transfers • Bacteria have a number of forms of recombination: • ___________ • ___________ • ___________ Conjugation Transformation Transduction

  39. Bacterial conjugation(DNA transferred through a mating process) • 2 bacteria connected by a tube calledthe sex pilus • F = fertility factor(ability to mate) • F+ is equal to being male (one thatgrows the sex pilus) • F– is equal to being a female • DNA passes through the sex pilusfrom the F+ to the F– • usually just the F factor, but sometimesother genes are carried along • F– becomes F+

  40. Figure 8.24: Griffith’s Transformation Experiment

  41. Transduction: • Transduction: host DNA carried from cell to cell by virus • Figure 8.28

  42. Biotechnology • Restriction Enzymes – enzymes found in bacteria that cut DNA at specific sequences.

  43. Cotton Plants with Bacillus gene inserted (left)

  44. Bioremediation

  45. Pharmaceuticals

  46. Figure 9.1

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