PLASMID DNA Plasmid is the small DNA molecule within a cell that is separated from chromosomal DNA It can replicate independently Plasmids are extrachromosomal unit that replicate autonomously within the suitable host. Plasmid are naked DNA not encapsulated in protein coat. No of DNA The number of identical plasmid differ from 1-1000 The number of copies in a cell is called copy number CONFORMATION OF PLASMID The plasmid DNA appears in different conformation Nick opened circular DNA Relaxed circular DNA Linear DNA Super coiled DNA Super coiled denatured DNA STRUCTURE OF PLASMID Plasmids are found as small circular double stranded DNA molecules in bacteria. The size of plasmid differ from 1-200kbp They are very small contains only addition genes that are required by the organisms for survival under certain circumstances such as antibiotic resistance gene. They also carry genes for their autonomous replication BIDIRECTIONAL REPLICATION The visualisation of this replicati...
MITOCHONDRIAL DNA(mt DNA)
- The mammalian mitochondrial DNA transmit through family gene line.
- The smaller circular chromosome found inside the mitochondria is called mit DNA.
- It is localised in mitochondria is called matrix and attached to the inner membrane of mitochondria.
- It is only a small portion of DNA in eukaryotic cell.
FORMS OF MITOCHONDRIAL DNA
- In animals mt DNA is in the form of double stranded closed circular molecule.
- In plants and protists mt DNA are generally circular with super helical twist.
- In unicellular organisms and few multicellular organisms mt DNA is in form of linear form.
SIZE
- mt DNA is smaller than DNA of bacteria or viruses
- In animal cell the length of circular mt DNA is 5-6µm with 16kb
- Human mt DNA has 16.569nucleotide base pairs
- Plants has 100kbp with length of 62µm
No of DNA molecules:
- The number of mt DNA molecule within a cell is called copy number
- It depend on the size of mitochondria
- In eukaryotic cell the no of mt DNA is proportional to number of mitochondria.
- Eg:Adult human=10^7mt DNA
- Trypanosomes=10000mt DNA
- Metazoan cells =1000-10000mt DNA
STRUCTURE OF mt DNA
- A human cell contains 100-10000 copies of mt DNA in somatic cells.
- Human mt DNA is double stranded and circular with 15000-17000bp.
- The two strands of circular mt DNA are
- Heavy strand
- Light strand
- The two strands differ in nucleotide content
H strands
- It has 28 genes
- It has 125rRNA,152 mRNA,14 tRNA and 12 polypeptide.
- The H strand rich in guanine residue
L strand
- The L strand rich in cytosine residue.
- It has 8tRNA and 1 polypeptide protein.
- It has 9 genes
- The human mt DNA super coiled to 37 genes for OXPHOS and mit protein synthesis
- They are 13 subunits in mt DNA
- They are 5 complex in mt DNA
- CI-NADH Ubiquinone oxidoreductase
- Succinate Ubiquinone oxidoreductase
- Ubiquinone Cytochrome C oxidoreductase
- Cytochrome C oxidase
- ATP Synthase
- These genes packed in tightly with few non –coding nucelotides.
- So this mitochondrial DNA lack introns.
- There are only few differences. Differences only in the form of interspecific or intraspecific.
- Replication of mt DNA is semiconservative
- Replication is by mt DNA polymerase
- Replication begins with formation of displacement loop or Dloop followed by synthesis of RNA primed DNA
DNA BARCODING
- The registered gene of 648bp length is used as standard gene barcode to identify animal group species.
- The registered gene is mitochondrial cytochrome C oxidase I CoI variation in species [Herber gene[CoI]
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