To determine which known species the unknown bacterial species is most closely related to, we need to compare the DNA sequences.
The provided DNA sequences are as follows:
- Unknown species: ACT GCA CCC
- Species I: ACA GCA CCG
- Species II: ACT GGT GGA
- Species III: ACA GCA GGG
- Species IV: ACT GCA CCG
Next, let's look for similarities:
-
Unknown (ACT GCA CCC) vs. Species I (ACA GCA CCG)
- Difference: 1 base (A vs. T) at position 1
-
Unknown (ACT GCA CCC) vs. Species II (ACT GGT GGA)
- Difference: 3 bases (C vs. G, C vs. T, C vs. A)
-
Unknown (ACT GCA CCC) vs. Species III (ACA GCA GGG)
- Difference: 2 bases (T vs. A, C vs. G)
-
Unknown (ACT GCA CCC) vs. Species IV (ACT GCA CCG)
- Difference: 1 base (C vs. G) at the last position
Based on the number of differences:
- Species I: 1 difference (most similar to unknown)
- Species IV: 1 difference
- Species III: 2 differences
- Species II: 3 differences (least similar)
Since both Species I and Species IV have the same number of differences (1) with the unknown, we will look at the actual sequences. The more similar the sequences are regarding specific position differences, the closer the relationship.
Species IV has the same first three bases (ACT GCA) as the unknown species, differing only at the last base.
Species I also has 1 difference but starts with "ACA", which is already a deviation from the unknown.
Thus, between Species I and Species IV, Species IV is indeed more similar overall due to maintaining the ACT GCA pattern.
Therefore, the unknown bacterial species is most closely related to Species IV.