Bacteria do possess a typical single circular chromosome comprising of a single circular molecule of DNA having associated proteins.
DNA and
Chromosomes
Bacteria
do possess a typical single circular
chromosome comprising of a single
circular molecule of DNA having associated proteins. It has been duly
observed that the chromosome is duly
looped, folded, and linked at
one or several points to the respective
plasma membrane. In reality, the DNA of
E. coli*, has approximately four
million base pairs, nearly 1 mm
in length, and almost 1000 times larger
than the entire cell. It may be observed that the DNA is rather quite thin, and
is closely packed inside the cell, thereby this apparently twisted and adequately
coiled macromolecule conveniently takes up merely 10% of the entire cell’s
volume.
Eukaryotic chromosome’s DNA is
generally found to be more tightly
condensed (i.e., coiled) in comparison to the prokaryotic
DNA.
The
following Table 6.1 records the comparison between the eukaryotic and the
prokaryotic chromosomes :
Table 6.1. Comparison Between Eukaryotic and
Prokaryotic Chromosomes
The
latest developments in genetic research has revealed that an extensive and
intensive clear cut understanding of the chromosomal
structure, besides the mechanism which enables the cell to afford turning
of genes on and off to yield
urgently required ‘crucial proteins’
when needed. Interestingly, the aforesaid modulation
of gene expression meticulously governs the following two vital operations in a living system, such as :
(a) differentiation of the eukaryotic cells right
into the various kinds of cells usually observed in the multicellular organisms, and
(b) on
going critical and specific activities in an ‘individual cell’.
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