The term rare amino acids is misleading in some respects. It refers to all those amino acids that are not incorporated into proteins. We already got to know some of them like ornithine or citrulline that are rather common intermediates of the basic metabolism. Roughly 220 different structures are known, most of which occur in plant cells in a free state though glutamate-, oxalate- or acetyl- derivatives can also sometimes be found.
Source: https://s10.lite.msu.edu/res/msu/botonl/b_online/e20/20e.htm
Hope this helps!
“There's a simple answer: Humans did not evolve from chimpanzees or any of the other great apes that live today. We instead share a common ancestor that lived roughly 10 million years ago. ... They're on an entirely different evolutionary path.”
If you need to use this rewrite it in your own words
<span>I think it is monosaccharides</span>
"In DNA thymine pairs with adenine, but in RNA uracil pairs with adenine. Similarities: - DNA and RNA are made up of monomers called nucleotides. - DNA and RNA both have 3 nitrogenous bases: Adenine, Cytosine and Guanine."
-enotes
Feb 18, 2009