Because their soft tissue and bones decay or get eaten before a fossil can be made.
Answer:
The near-UV CD range (>250 nm) of proteins delivers info on the define configuration. The indications found within the 250–300 nm section are because of the engagement, dipole alignment and also the environment of the encircling atmosphere of the essential amino acid, tyrosine, aminoalkanoic acid (or S-S disulfide associations) and essential amino acids. In contrast to far-UV CD, the near-UV CD variation can't be allotted to any specific 3D configuration. Relatively, near-UV CD varieties offer essential info on the character of the prosthetic teams in proteins, e.g., the pigment teams in hemoprotein and cytochrome.
All the cells in a person's body have the same DNA and the same genes. However, the difference between cells in different tissues and organs is that the "expression" of the genes differs between cells. Expression means that the message from the DNA is being copied and made into protein.
