The total number of possible amino acid sequences in a polypeptide chain is staggering. Given that there are 20 amino acids, potentially there could be20100 different amino acid sequences just for polypeptides only 100 amino acids in length. However, the actual number of different polypeptides occurring in organisms is only a tiny fraction of this potential. What insight does this finding provide into the evolutionary process?

Here is some information about the sequences: There are two images given; one with sequences and the other with a figure. All these sequences, “SEQUENCE_21” to “SEQUENCE_27” are in the same subfamily or “clade” of a large phylogenetic alignment of all Rab proteins in these three species (see “Image with a figure” for a full view of gene family in humans, plants and yeast, see the “D” branch towards the bottom of the tree in Figure). “SEQUENCE_28” is a different Rab protein (actually it is the Rab39 protein at the bottom of the tree). “SEQUENCE_21” is from yeast. “SEQUENCE_22” to “SEQUENCE_25” are from the plant, Arabidopsis. “SEQUENCE_26” and “SEQUENCE_27” are from humans. Question: Based on the information above, what can you speculate about the possible evolution of the genes that “SEQUENCE_21” to “SEQUENCE_27” represent?

What are two reasons for the wide variation in genome sizes among eukaryotic species?

Would you be more likely to find single nucleotidepolymorphisms (SNPs) in the protein-coding or in thenoncoding DNA of the human genome?