A portion of the amino acid sequence of an enzyme from a worm is shown below.
-Q-Q-Q-N-N-N-C-C
Analyze the same portion of the same enzyme taken from several other organisms. Place them in order from most closely related to the worm most distantly related to the worm.
-Q-R-Q-N-S-S-C-C- organism X
-Q-Q-Q-N-N-S-C-C- organism Y
-Q-Q-R-N-S-N-C-C- organism Z
a. Z,Y,X
b. Y,Z,X
c. X,Z,Y**
d. Y,X,Z
What was it? Was B right?
To analyze the portion of the amino acid sequence and determine the order of relatedness to the enzyme from the worm, you can compare the amino acid residues and identify their similarities and differences.
Let's break down the portion of the amino acid sequence for each organism:
Organism X: -Q-R-Q-N-S-S-C-C-
Organism Y: -Q-Q-Q-N-N-S-C-C-
Organism Z: -Q-Q-R-N-S-N-C-C-
To determine their relatedness to the worm, we need to compare the amino acid residues one by one:
The first residue in all three organisms is the same (Q), so we can't differentiate them based on that.
The second residue differs between the worm and all three organisms (w = R, X = Q, Y = Q, Z = Q). This tells us that organism X, organism Y, and organism Z all have a different amino acid residue in the second position compared to the worm. However, organisms Y and Z have the same residue between each other.
The third residue is the same between the worm and organism X (Q). Organism Y has a different residue (Q) and organism Z has a different residue (R).
The fourth residue is the same between the worm, organism Y, and organism Z (N). Organism X has a different residue (S).
The fifth residue differs between the worm and all three organisms (w = N, X = S, Y = N, Z = S). Organism X and organism Z have the same residue between each other.
The sixth residue differs between the worm and all three organisms (w = N, X = S, Y = S, Z = N). This tells us that organism Y has a different amino acid residue in the sixth position compared to the worm. Organism X and organism Z have the same residue between each other.
The seventh residue is the same between the worm and all three organisms (C).
The eighth residue is the same between the worm and all three organisms (C).
Based on these comparisons, we can determine the order of relatedness:
The most closely related organism to the worm is organism X because it has the fewest differences in the amino acid sequence.
The second most closely related organism to the worm is organism Z because it has a slightly higher number of differences compared to organism X.
The most distantly related organism to the worm is organism Y because it has the highest number of differences in the amino acid sequence.
Therefore, the correct answer is c. X,Z,Y.