Amino acids gene duplication

G-CSF may be related to IL-6 because both the number and size of in-trons and exons in these two genes are similar. Furthermore, amino acid residues 20-85 in G-CSF and 28-91 in IL-6 have 26% homology, and the positions of four cysteine residues in these regions are precisely conserved. Whilst the IL-6 gene is located on chromosome 7pl5, it may be that the two genes arose from duplication and have since diverged. 

Fig. 1 shows sections from the amino acid sequences of the two subunits, using the single-letter notation (see p. 60). A common precursor gene was probably duplicated at some point in evolution. The two genes then continued to develop further independently of each other through mutation and selection. 

Like IFN-a, IFN-co genes have duplicated to high copy numbers in ruminants but not in humans [64], Unlike IFN-a, IFN-co protein is 172 amino-acid residues long and is capable of eliciting similar biological responses in vitro as compared to other type I IFNs [36],... 

Much of the amino acid sequence in the first half of the ferredoxin chain is repeated in the second half, suggesting that the chain may have originated as a result of gene duplication. Many invariant positions are present in the sequence, including those of the cysteine residues forming the Fe-S cluster. Ferredoxins with single Fe4S4 clusters are also known 270... 

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