Gene structure, expression and regulation in prokaryotes

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Bachelors Degree Biology (Gene structure, expression and regulation in prokaryotes) Mind Map on Gene structure, expression and regulation in prokaryotes, created by Natalina Laria on 28/05/2016.
Natalina Laria
Mind Map by Natalina Laria, updated more than 1 year ago
Natalina Laria
Created by Natalina Laria almost 8 years ago
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Resource summary

Gene structure, expression and regulation in prokaryotes
  1. Bacterial genome
    1. Circular chromosomal DNA
      1. Typically a few million base pairs long
        1. Most bacterial species contain a single type of chromosome
          1. A few thousand different genes are interspersed throughout the chromosome, genes separated by short, intergenic regions
            1. One origin of replication is required to initiate DNA replication
              1. No nucleus
                1. Haploid (one copy of every gene)
                  1. Small compact and repetitive
                  2. Plasmids
                    1. Replicate independently
                      1. Can integrate into chromosome
                        1. Not essential for survival
                          1. Fewer genes
                          2. Gene organisation in Prokaryotes
                            1. Organised into operons
                              1. A set of genes encoding proteins participating in the same metabolic pathway
                              2. Transcribed as polycistronic mRNA
                                1. Several proteins under influence of one promoter
                                  1. Advantage: timing and amounts
                                    1. Disadvantage: mutations inflexible
                                2. Transcription and translation
                                  1. Occur at the same time in the “same cellular compartment”
                                    1. Translation of an mRNA may begin before the mRNA is completely transcribed
                                      1. Transcription unit
                                        1. Promoter
                                          1. Important in initiation
                                            1. Conserved sequence of nucleotides in a DNA strand that is a binding site for RNA polymerase
                                              1. Position and orientation of the promoter determines which strand is transcribed and where transcription starts
                                              2. RNA coding region
                                                1. Terminator
                                                2. Transcription
                                                  1. Copying of template DNA strands
                                                    1. Strands grow in a 5' to 3' direction
                                                      1. RNA polymerases can initiate strand growth
                                                        1. DNA polymerases require a primer
                                                          1. Occurs in 3 phases
                                                            1. Initiation
                                                              1. Sigma factors recognise the promoter to initiate transcription
                                                                1. Promoter recognition Formation of transcription bubble Creation of bonds between rNTPs Escape from transcription apparatus from promoter
                                                                2. Elongation
                                                                  1. Termination
                                                                    1. Rho-independent Characterised by 1.) inverted repeats 2.) string of adenines -> slow down polymerase -> formation of hairpin structure followed by a string of uracils
                                                                      1. Rho-dependent 1.) DNA region, that slows polymerase down 2.) Unstructured region -> binding site for rho protein, catches up, helicase activity
                                                                        1. NO HAIRPIN STRUCTURE
                                                                  2. Translation
                                                                    1. Genetic code is read in triplicate but can be read in different frames
                                                                      1. Genetic code and mutations
                                                                        1. Silent mutation: the base change does not result in a protein change
                                                                          1. Mis-sense mutation: a single amino acid is changed
                                                                            1. Nonsense mutation: an amino acid codon is changed to a stop codon
                                                                              1. Frameshift mutation: insertion or deletion of a number of nucleotides that is not a multiple of three
                                                                            2. Different phases
                                                                              1. Charging of tRNA
                                                                                1. Amino acid links to tRNA
                                                                                  1. tRNA then binds its codon in RNA
                                                                                    1. Net result = amino acid is selected for by its codon
                                                                                2. Initiation
                                                                                  1. Requires ribosomes and initiation factors
                                                                                    1. Complementary base-pairing between the Shine-Dalgarno sequence on the mRNA and the rRNA occurs
                                                                                      1. Small subunit binds to Shine-Dalgarnonsequence with the help of IF3
                                                                                        1. Then fMet-tRNA binds to initiation codon with the help of IF1, IF2 and GTP
                                                                                          1. This is called the 30s initiation complex
                                                                                            1. Then IFs are removed and large subunit is added
                                                                                              1. This is called the 70s initiation complex
                                                                                                1. In summary the ribosome has been assembled on the mRNA and the first tRNA is attached to the initiation codon
                                                                                    2. Elongation
                                                                                      1. Termination
                                                                                        1. Once ribosome reaches stop codon RFs are recruted
                                                                                  2. Types of RNA found in prokaryotes
                                                                                    1. mRNA
                                                                                      1. tRNA
                                                                                        1. rRNA
                                                                                        2. Lac operon
                                                                                          1. lacZ
                                                                                            1. b-galactosiadase
                                                                                              1. Splits lactose into galactose and glucose
                                                                                            2. lacY
                                                                                              1. Lactose permease
                                                                                                1. Transports lactose into cell
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