- AX-ray crystallography.
- BElectron microscope.
- CUltracentrifuge.
- Dlight microscope.
Explanation:
Nucleotide arrangement in DNA can be seen by X-ray Crystallography. X-ray crystallography is used to determine 3D structures of macromolecules like proteins, nucleotides, etc. The basic principle of this techniques is that the wavelength of x-rays depends on the distance between the atoms of the structures which makes it useful for determining their arrangement.
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$I.$ An Association of two species where one is benefitted and other remains unaffected is called mutualism.
$II.$ An interspecific association where both partners derive benefit from each other is called commensalism.
$III.$ A direct food relation between two species of animals in which one animal kills and feeds on another is referred as predation.
$IV.$ A relationship between two species of organisms where both are partners are
benefitted from each other is called symbiosis