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Microbial Genetics

Slides are adapted from Dr. Gary Andersen, Curtis Smith, KCKCC Reference: Chapter 7,8 from (Black, J., 2005). Microbial Genetics. Genomes – the total of the genetic material in a cell.

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Microbial Genetics

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  1. Slides are adapted from Dr. Gary Andersen, Curtis Smith, KCKCC Reference: Chapter 7,8 from (Black, J., 2005) Microbial Genetics

  2. Genomes – the total of the genetic material in a cell. Gene - The unit of heredity for a given genetic trait. The site on a DNA molecule that carries the code for a certain cell function. Viruses – 4 or 5 genes, E. coli – 4228 genes, Human ~ 31,000 genes. Basic Units of Genetics

  3. I. Nucleic acids are located in the nucleoid of bacteria, and the nucleus of eukaryotes. There are 2 kinds of nucleic acids: RNA & DNA. Nucleic Acids Ruptured E. coli cell showing DNA

  4. CHARACTERISTICS OF DNA DNA(deoxyribonucleic acid) is made of subunits called nucleotides. Nucleotides are made of 3 components. These 3 components are linked together with a covalent bond. E. Coli = 4.6 million nucleotide pairs (~1mm) Corn = 2.5 billion nucleotide pairs Human = 3 billion nucleotide pairs (2nm wide by 2 meters long) DNA

  5. Maintains the code with high degree of fidelity. (double strand assures accurate replication) Provides a method for introducing a high degree of variety. (unlimited variety of sequences possible) Significance of DNA Structure

  6. Phosphate group - Phosphate functions as a structural part of nucleic acids. 1. COMPONENT 1 - Phosphate

  7. 2, DEOXYRIBONUCLEIC ACID Ribose - A five carbon sugar that functions as part of the DNA backbone (ie. structural). “2, Deoxy” means without oxygen on the number 2 carbon atom. 2. COMPONENT – Ribose Sugar

  8. NITROGEN CONTAINING BASES Function: express genetic information. Composition : 2 PURINES: ADENINE (A) GUANINE (G) double ring structures 2 PYRIMIDINES: THYMINE(T) CYTOSINE(C) single ring structures 3. COMPONENT – Nitrogen Bases

  9. Nucleotide Base Composed of one Nitrogen base, one Deoxyribose, and one Phosphate group Adenine (Nitrogen base) Deoxyribose Phosphate

  10. 4 Nucleotides T A C G

  11. DNA Structure

  12. 4. DNA is a double helix (there are 2 strands of DNA) which are intertwined with 5 base pairs per turn. 5. DNA has complimentarity that is A always bonds with T and G always with C 6. DNA is always antiparallel. The 2 strands of DNA are always oriented in opposite directions. ( 5’ PO3 end – 3’ OH end) http://www.umass.edu/microbio/chime/dna/dna53.htm DNA Structure

  13. DNA Bonds

  14. 3-D Image ofDNA

  15. RIBONUCLEIC ACID Similar to DNA except: 1. RNA is single stranded 2. RNA has a ribose sugar instead of deoxyribose. (Oxygen on #2 C). 3. RNA has URACIL (u) instead of thymine 4. RNA is always shorter than DNA, ~ 1,000 nucleotides in length B. RNA

  16. 1. rRNA (ribosomal) - comprises the ribosome (site of protein synthesis). (60% of a ribosome is made of RNA, the rest is protein). 2. tRNA (transfer) carries amino acids to the ribosome during protein synthesis. Also known as the “ANTICODON” 3. mRNA (messenger) - a complimentary strand of RNA equal in size to 1 gene (normally ~1,000 nucleotides). “CODON” - coded info from DNA (bound for the ribosome) C. FUNCTIONS OF RNA

  17. There are 3 parts to the flow of information in all cells. TranscriptionTranslation DNA -------------mRNA-----protein Replication THE CENTRAL DOGMA OF BIOLOGY “Francis Crick – 1956”

  18. Central Dogma of Biology

  19. 1. Where 2 parental strands of DNA are copied into 2 daughter strands. Rate = 1,000 nucs per seconds without error. This leads to binary fission in bacteria. Cell Division) = 2 daughter cells 2. Each cell receives 1 parental strand and 1 daughter strand. (semiconservative replication) DNA REPLICATION GA sp 08

  20. As the two replication forks meet, the two new chromosomes separate—each containing one new and one old strand

  21. Replication bonding

  22. Replication Fork

  23. DNA unwinds using the enzyme DNA Helicase SSBP holds the 2 strands apart (single strand binding proteins) Note: 2 replication forks. DNA replication is considered bi-directional replication. 1. EVENTS IN DNA REPLICATION

  24. Polymerization requires DNA Polymerase (POL III) which is an enzyme that synthesizes 2 nucleotide strands (daughter strands) from 2 parental (templates) strands. DNA exonuclease (POL I) removes any mistaken base pairs. DNA ligase seals any gaps and joins the 2 strands together. DNA REPLICTION CONT’D

  25. DNA Replication Enzymes at Work

  26. Steps in Replication

  27. Replication of DNA cont’d

  28. Sit back!! We’re watching a movie for a while (But don’t expect too much)

  29. Let’s watch some “interesting”, academic movies • Movie 1 • Movie 2 • Movie 3

  30. There are 3 parts to the flow of information in all cells. TranscriptionTranslation DNA --------------mRNA---------protein Replication THE CENTRAL DOGMA OF BIOLOGY

  31. 2nd part of the central dogma of biology 1st step in gene expression (i.e.protein synthesis). The cells genetic plan contained in DNA is transcribed into a complimentary base sequence called messenger RNA (mRNA). The region of DNA that produces or serves as a template for mRNA is called a gene. A gene normally consists of around 1,000 base pairs. It is the smallest segment of DNA that codes for mRNA. B. TRANSCRIPTION

  32. 5. RNA polymerase is the enzyme responsible for making mRNA TRANSCRIPTION CONT’D

  33. 7. Example: DNA A T G C C G DNA T A C G G C mRNAA U G C C G 8. mRNA is a blueprint of DNA or a transcript or code. 9. One code word consists of three letters. Transcription continued

  34. Animation of Transcription • Movie 1 • Movie 2 • Movie 3

  35. Translation is the 3rd part of the central dogma of biology (2nd step in gene expression or protein synthesis). After transcription, the coded information in mRNA is translated into an enzyme (protein). This process takes place on the ribosome. Note that the ribosome is made of rRNA and protein. C. TRANSLATION

  36. Translation Graphic

  37. tRNA STRUCTURE tRNA utilizes the information in mRNA to determine the sequence of amino acids in a protein. tRNA has a cloverleaf shape. The amino acid end binds one specific amino acid in the cytoplasm. The anticodon end pairs with the codon on mRNA. TRANSLATION CONT’D

  38. Transfer RNA Structure

  39. The mechanics of translation Initiation; mRNA bumps into the small subunit and triggers the two ribosomal subunits to bind together. The first tRNA anticodon (UAC) carrying the amino acid methionine hydrogen bonds with the codon AUG on mRNA. TRANSLATION CONT’D

  40. b. Elongation – The second tRNA binds to the second code word on mRNA. A peptide bond forms between the two amino acids. The first tRNA leaves, and the enzyme translocase moves the ribosome down one code word of mRNA at a time. This repeats ~ 300X. TRANSLATION CONT’D

  41. C. In termination, one of three possible stop codons is reached. The last tRNA falls away and the two ribosomal subunits fall apart. TRANSLATION CONT’D

  42. 61 sense codons for 20 amino acids 3 nonsense (or stop codons) total codons Pg 180 (Black, J., 2005) d. The Genetic Code

  43. The Genetic Code

  44. Steps in Protein Synthesis

  45. Steps in Protein Synthesis

  46. Steps in Protein Synthesis

  47. Steps in Protein Synthesis

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