DNA

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Author:
kkincaid
ID:
176807
Filename:
DNA
Updated:
2012-10-12 15:24:28
Tags:
Microbiology
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Description:
Exam 2
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  1. DNA
    Genetic information used by all living organisms
  2. Microbial gene
    • 4,000
    • Human genome - 22.000
  3. How many genes are in the genome of E. coli?
    about 4000 genes
  4. DNA function as:
    • Long term information storage-DNA polymerase
    • Blueprint for gene expression-Gene expression basics
  5. DNA polymerase
    Replicates chromosome form origin of replication sites prior to cell division
  6. Gene Expression Basics
    • 1. DNA (gene) transcribed by RNA polymerase into mRNA (e.g. mRNA)
    • 2. mRNAs tanslated on ribosome into PRO
    • -mRNA read as 3 nt codons
    • -codon sequence specifies protein's amino acid sequence
  7. Important roles of DNA and RNA
    • Cell Division-Replicatioin
    • Gene Expression-Transcription & Translation
  8. Mutation
    • Occur during DNA replication
    • Contribute to species and strain differences
  9. All RNA is _____ from a _____ template.
    All RNA is transcribed from a DNA template
  10. tRNAs
    Carry amino acids and can read codons in mRNA
  11. Where does translation occur
    Ribosomes
  12. Codon
    3 nucleotides that code for specific amino acids sequence
  13. Translation
    • Occurs on ribosomes
    • 1.Ribosomes attaches to mRNA
    • 2. tRNA anticodon attaches to the matching mRNA codon
    • 3. A second tRNA attaches at next codon on mRNA
    • 4. Peptide bind forms enzymatically between first two amino acids
    • 5. Ribosome moves along mRNA as next tRNA attaches to next codon
  14. Protein lengthened until ribosome reads
    stop codon
  15. Genetic Code
    lists all codons and which amino acid they specify
  16. Transcription
    DNA---RNA from DNA template
  17. tRNA
    Can read codons in mRNA
  18. Translation
    • Occurs on ribosome in the cytoplasm
    • Anticodon on the tRNA pairs with the codon of the mRNA
    • froms peptide bonds that connect amino acids
    • 1.Initiation 2. Elongation 3.Stop Codon -- release of PRO
  19. Genetic Code
    Lists codons and amino acids they specify
  20. Transcription and translation (prokaryotes)
    Occur simultaneously in prokaryotes because there are no organelles to separate process
  21. Vertical gene transfer
    Mother to daughter
  22. Microbial Diversity is generated
    • 1. Mutations in DNA
    • 2. Horizontal gene transfer -- Donor cell to recipient cell which produces and a recombinant cell
  23. Primary source of genetic diversity in microbes
    Horizontal gene transfer
  24. Types of Horizontal gene transfer
    • 1. Transformation
    • 2. Transduction
    • 3. Conjugation
  25. Transformation
    • Griffith
    • Free DNA taken up by recipient cell and integrated into that cells genome
    • Only competent cells can take up DNA
    • Use in genetic engineering
    • Provided evidence that DNA (not protein) was the ling sought after genetic material
  26. Competence factor
    Expression by recipient or chemical treatment
  27. Bacterial Transformation
    • 1. Naked DNA fragments from disintegrated cells (DNA released by dead cells) in the area of potential recipient cells
    • 2. Entry of naked DNA into competent, correct genus, physiologic condition cell
    • 3. Recombination, Some DNA fragments replace original host cell DNA. Now genetically transformed and will pass to offspring
  28. transduction
    • Bacteriphage transfer of DNA from donor bacteria to recipient
    • Phage injects DNA into bacterial cell
    • Bacterial DNA is fragmented as phage replicates
    • Fragmented of bacterial DNA is incorporated into phage head. Bacterial cell is lysed, and new phage is released
    • Phage contained DNA infects new cell
    • Genes from first bacterial host are incorporated into chromosome of new host
  29. Transduction:Virus transfers DNA
    • Bacterophage virus injects nucleic acid, may kill quickly (lytic) or integrate into host chromosome (lysogenic)
    • Virus life cycle always involved packaging of viral genome into new virons
    • DNA from host cell is integrated into viral DNA during packaging
    • Phage transfers this new DNA to another host cell/bacteria
    • Could be gene or toxin/antibiotic resistance
  30. When does transduction occur?
    As bacterial DNA from donor (infected) cell is mis-packaged into new virus
  31. Conjugation
    • Plasmid transfer via conjugation (sex) pillus -- transfers largest amount of DNA
    • F+ (male) transfer plasmid to F- (female)
    • Plasmid duplicated in new cell
  32. Bacterial conjunction
    • Transfers plasmid DNA
    • both cells then contain plasmid
  33. Plasmid
    • Small, circular, self-replicating extra-chromosomal DNA
    • Specialized non-essential genes (dont need to survive)
    • Often contain antibiotic resistance genes
    • Important molecular biology tool
  34. Transposons
    "Jumping" DNA sequence, move randomly between plasmids, chromosomes
  35. Transposons Composed
    • Transposase gene allows transposition
    • Recognition (insertion) sequences at ends
    • often include resistance gene(s)

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