Ultra Structure of Chromosome

Ultra Structure of Chromosome
Eukaryotic chromosomes are composed of chromatin, a complex of DNA and protein and less amount of RNA.
Deoxyribonucleic Acid (DNA)
The DNA of a chromosome is one very long double stranded fiber, duplex which extend unbroken through the entire length of chromosome.
A typical human chromosome contain about 140 million nucleotide in its DNA.
Size
If a strand of DNA from a single chromosome were laid out in a straight line, it would more than 7 feet long (2 meter). It is too much long to fit into a cell. In the cell, however, the DNA is coiled, thus fitting into a much smaller space.
Nucleosome
DNA resemble a string of beads. Even 200 nucleotides, the DNA duplex is coiled around a core eight histone proteins forming a complex known as Nucleosome.
Protein
Histones are positively charged proteins due to an abundance of the basic aminoacids, arginine and lysine. They are thus strongly attached to the negatively charged phosphate groups of the DNA.
Further coiling occurs when the string of nucleosomes wraps up into higher order coils called Super Coils.
Heterochromatin
Highly condensed portions of the chromatin are called Heterochromatin.
Euchromatin
The reminder of the chromosome called Euchromatin is condensed only during the cell division.
Karyotype
The particular array of chromosome which an individual possess is called the Karyotype in which chromosomes are paired by matching bonding and arranged by size and shape.
Applications

• Karyotypes show marked differences among species and sometime even among individuals of the some species.
• It help in determining many issue as the culprits of difference offences and settle the disputed paternity.
• It help in detecting genetic abnormalities, arising from extra or lost chromosome.