Question 2 of 4

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 to 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

To determine the order of organisms from most closely related to the worm to most distantly related, we need to compare the amino acid sequences of the enzyme.

Let's analyze the sequence from each organism and compare them to the worm's sequence:

- 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-

Comparing each position in the sequence, we can identify the differences:

- Position 1: X has an "R," Y and Z have "Q."
- Position 2: X and Y have "Q," Z has "R."
- Position 3: X and Y have "Q," Z has "R."
- Position 4: All organisms have "N."
- Position 5: X has "S," Y and Z have "N."
- Position 6: X and Y have "S," Z has "N."
- Position 7: All organisms have "C."
- Position 8: All organisms have "C."

Based on these comparisons, we can conclude that organism X has the closest similarity to the worm since it only differs at positions 1, 2, 3, and 5. Organism Y differs at positions 1, 2, 3, and 6, and organism Z differs at positions 1, 3, 5, and 6.

Therefore, the correct order from most closely related to most distantly related is:

B. Y, Z, X

To determine the order of the organisms from most closely related to the worm to most distantly related, we need to compare their amino acid sequences to that of the worm.

Looking at the given amino acid sequences:
- Organism X has Q-R-Q-N-S-S-C-C
- Organism Y has Q-Q-Q-N-N-S-C-C
- Organism Z has Q-Q-R-N-S-N-C-C

We can see that organism Z has the most similarities with the worm's sequence, with the only difference being a change from "Q" to "R" at the third position. Therefore, organism Z is the most closely related to the worm.

Next, we compare organisms X and Y. Both have some differences with the worm's sequence, but organism X has an additional change from "N" to "S" at the fourth position, whereas organism Y has no additional changes compared to the worm. Therefore, organism Y is more closely related to the worm than organism X.

Based on this analysis, the correct order from most closely related to most distantly related to the worm is:

C. X, Z, Y