Presentation is loading. Please wait.

Presentation is loading. Please wait.

Unit 3c Microbial Genetics. Genetics: the science of heredity Genome: the genetic information in the cell Genomics: the sequencing and molecular characterization.

Similar presentations

Presentation on theme: "Unit 3c Microbial Genetics. Genetics: the science of heredity Genome: the genetic information in the cell Genomics: the sequencing and molecular characterization."— Presentation transcript:

1 Unit 3c Microbial Genetics

2 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 Chromosomes and _________ Chromosomes are structures containing the DNA Plasmids

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

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 Simultaneous transcription and translation in bacteria


31 Becomes mRNA (messenger RNA) – this has the code for how to build a protein _____________ ____________ Connects RNA nucleotides together (like DNA polymerase) RNA Polymerase

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


34 Polypeptide Chain – all the amino acids who together



37 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

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

39 Ames Test uses bacteria as carcinogen indicators (figure 8.22) Many known mutagens have been found to be carcinogens

40 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

41 An overview of genetic flow ….figure 8.2

42 Bacterial gene transfers Bacteria have a number of forms of recombination: –___________ Conjugation Transformation Transduction

43 Bacterial conjugation (DNA transferred through a mating process) 2 bacteria connected by a tube called the sex pilus F = fertility factor (ability to mate) F+ is equal to being male (one that grows the sex pilus) F– is equal to being a female DNA passes through the sex pilus from the F+ to the F– usually just the F factor, but sometimes other genes are carried along F– becomes F+

44 Figure 8.24: Griffith’s Transformation Experiment

45 Transduction: Transduction: host DNA carried from cell to cell by virus Figure 8.28

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

47 Cotton Plants with Bacillus gene inserted (left)

48 Bioremediation

49 Pharmaceuticals

50 Figure 9.1

51 DNA in diagnosis 4. Nucleic acid hybridization Basis of DNA probes –Short segments of ssDNA that are complementary to the desired gene Complementary strands of known DNA separated by heat One side marked with fluorescent dye DNA of unknown bacteria separated by heat Will hybridize with fluorescent strand of known DNA if same kind. After rinsing away unbound DNA, a fluorescent DNA double strand will remain Can hunt for complementary DNA within a massive amount of material, such as food

52 DNA-DNA hybridization (fig. 10.15)

53 DNA probe to detect Salmonella Why use E. coli ? Easily grown & researchers are familiar with its genetics Figure 10.16

54 DNA probe, continued


56 DNA Chips (figure 10.17) An array of DNA probes arranged in a DNA chip can be used to identify pathogens

57 BUT should we?

Download ppt "Unit 3c Microbial Genetics. Genetics: the science of heredity Genome: the genetic information in the cell Genomics: the sequencing and molecular characterization."

Similar presentations

Ads by Google