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Bacterial Genome
- Genome (of a cell/virus) is its entire genetic complement (inc. genes and sequences that connect all genes together)
- All animals, plants and bacteria use DNA to carry their
genetic info. Some viruses use RNA, either ss/ds DNA
or RNA
- DNA Bases A=T and C=G (not equal in ss viruses)
- Most prokaryotes contain one ds circular DNA. Some have
more than 1 (e.g. Vibrio Cholerae). Some are linear
- Chromosomes are localized in a a region called the Nucleiod
- Chromosomal DNA is folded into loops 50,000-10,000 bps
long, held in place by protein and RNA, then folded into a
compact mass.
- Stretched out DNA would measure 1.6mm
- Stretched out DNA would measure 1.6mm
- Chromosomal DNA is folded into loops 50,000-10,000 bps
long, held in place by protein and RNA, then folded into a
compact mass.
- Chromosomes are localized in a a region called the Nucleiod
- Most prokaryotes contain one ds circular DNA. Some have
more than 1 (e.g. Vibrio Cholerae). Some are linear
- DNA Bases A=T and C=G (not equal in ss viruses)
- The human DNA encodes about 30,000 genes
- All animals, plants and bacteria use DNA to carry their
genetic info. Some viruses use RNA, either ss/ds DNA
or RNA
- Plasmind... a small circular molecule of DNA
- Exists independently of the chromosome
- Can be as small as 1-2 Kb or over 100Kb.There can be one or over
300 copies of each plasmid
- They code for their own replication and usually have one or more traits
- Genes that are carried on the plasmid are NOT essential for normal metabolism
- Fertility (F) Factors
- Carry instructions for conjugation, allowing genes to transfer from one
bacteria to another
- Carry instructions for conjugation, allowing genes to transfer from one
bacteria to another
- Resistance (R) Factors
- genes that give resistance to antibiotics for heavy metals. important in
medicine as they are why antibiotics stop working to treat infections
- Due to the spread of R-factor plasmids many antibiotics can't be used
- 98% of s.aureus strains are resistant to penicilin
- 98% of s.aureus strains are resistant to penicilin
- Due to the spread of R-factor plasmids many antibiotics can't be used
- genes that give resistance to antibiotics for heavy metals. important in
medicine as they are why antibiotics stop working to treat infections
- Bacteriocin Factors
- carry genes for toxins that kill other bacteria
and allow a bacteria to kill the competition
- carry genes for toxins that kill other bacteria
and allow a bacteria to kill the competition
- Virulence Factors
- carry genes fro structures, enzymes and toxins that enable a bacteria
to become pathogenic and cause disease
- Shigella has 230 Kb virulence plasmid that allows it to attach & invade
the human gut and cause dysentry
- can also be found in salmonella and E.coli sp
- can also be found in salmonella and E.coli sp
- Shigella has 230 Kb virulence plasmid that allows it to attach & invade
the human gut and cause dysentry
- carry genes fro structures, enzymes and toxins that enable a bacteria
to become pathogenic and cause disease
- Degradative Factors
- carry genes for the breakdown of chemicals (e.g. oils,
xylene) can be useful economically & enviromentally
- carry genes for the breakdown of chemicals (e.g. oils,
xylene) can be useful economically & enviromentally
- Cryptic Plasmids
- Function is unknown
- Function is unknown
- Exists independently of the chromosome
- Genome Organisation
- Not all DNA codes for protein. some is just for space between genes
- Genes can run left-right or right-left
- Genes can run left-right or right-left
- Coding & Non-coding
- DNA has 2 strands coding and non-coding strand
- Coding Strand matches the sequence of the mRNA. It has the sequence that matches the bases
that code the protein and makes sense when we read it
- Non-coding strand is copied by RNA Polymerase (also known as the template strand)
- Coding Strand matches the sequence of the mRNA. It has the sequence that matches the bases
that code the protein and makes sense when we read it
- DNA has 2 strands coding and non-coding strand
- RNA Polymerase can initiate a new RNA strand
- DNA Polymerase can not start a new strand, they need a primer, a starting point they
can then extend from a 3'end
- DNA Polymerase can not start a new strand, they need a primer, a starting point they
can then extend from a 3'end
- Organisation of Prokaryotic Genes
- DNA is transcribed into mRNA by RNA Polymerase (enzyme_
- The promoter sequence, upstream of the start of the RNA coding seqeunce is where RNA Polymerase interacts to begin transcription
- The promoter consists of 2 sequences. One if found 35 bases before the start of the mRNA and one is found 10 bases before the start.
- Referred to as -35 and -10 promoter sequences
- -35 consensus consequence TTGACA
- -10 consensus consequence TATAAT
- TTGACA ----17+/- ---- TATAAT
- Beyond the promoter is the first base that RNA Polymerase turns into mRNA
- Can only be found experimentally
- mRNA...in bacteria messages can be polycistronic (one mRNA encodes for several proteins)
- Eukaryotes do not do this. One mRNA encodes for ONLY one protein
- Eukaryotes do not do this. One mRNA encodes for ONLY one protein
- Can only be found experimentally
- -35 consensus consequence TTGACA
- Referred to as -35 and -10 promoter sequences
- The promoter consists of 2 sequences. One if found 35 bases before the start of the mRNA and one is found 10 bases before the start.
- The promoter sequence, upstream of the start of the RNA coding seqeunce is where RNA Polymerase interacts to begin transcription
- DNA is transcribed into mRNA by RNA Polymerase (enzyme_
- Transcription
- 1. RNA Polymerase attaches itself to the DNA strand (before the promoter)
- 2. Recognises the promoter and unzips the DNA
- 3. Sigma Factor is released from the RNA Polymerase
- 3. Sigma Factor is released from the RNA Polymerase
- 2. Recognises the promoter and unzips the DNA
- CodIng regions are EXONS. Non-coding regions are INTRONS
- 1. RNA Polymerase attaches itself to the DNA strand (before the promoter)
- Translation
- Ribosome (rRNA & Porteins) translate mRNA into protein
- In Prokaryotes ribosomes bind to mRNA at a sequence known as Shine Dalgarmo Sequence
- Shine Dalgarmo Sequence (a piece of mRNA that is complementary to the 3'end of the 16S RNA of the (ribosome)
- AGGAGG is the consensus sequence ad is 4-7 bases 5' of the start codon
- In prokaryotes this is not always AUG (Methionine)
- Ribosomes read the mRNA and specific tRNA molecules incorporate the correct amino acid into the group peptide chain
- Each tNA has a anti-codon that aches the codon in the mRNA
- there is one start codon: AUG (fmet)
- There are 3 stop codons: UAA UGA UAG
- There are 3 stop codons: UAA UGA UAG
- there is one start codon: AUG (fmet)
- Each tNA has a anti-codon that aches the codon in the mRNA
- Ribosomes read the mRNA and specific tRNA molecules incorporate the correct amino acid into the group peptide chain
- In prokaryotes this is not always AUG (Methionine)
- Shine Dalgarmo Sequence (a piece of mRNA that is complementary to the 3'end of the 16S RNA of the (ribosome)
- In Prokaryotes ribosomes bind to mRNA at a sequence known as Shine Dalgarmo Sequence
- Ribosome (rRNA & Porteins) translate mRNA into protein
- Not all DNA codes for protein. some is just for space between genes
- Not all DNA is genes coding for proteins
- Some DNA is intragenic - has no known function (might just be a spacer DNA between genes)
- There are other structures that can be found in prokaryotic DNA- phages, transposons and intergrons
- Some DNA is intragenic - has no known function (might just be a spacer DNA between genes)
- In TRANSFORMATION, a recipient cell takes up DNA from the enviroment
- Discovered by Fredrick Griffith (1928)
- Discovered by Fredrick Griffith (1928)
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