You will use the cytochrome c oxidase I (COI) gene to investigate relationships among salmon species. (This gene encodes a protein that functions in the mitochondrial electron transport chain.) You will compare the COI gene sequences from your salmon test samples to the standard sequences for each salmon species. In order for the COI gene to be useful for distinguishing among the different salmon species, which three statements must be true?

a) The COI gene must be conserved enough that the sequences can be aligned for comparison.

b) The COI gene must not contain any insertions or deletions.

c) The COI gene must be present in Pacific salmon but not in Atlantic salmon.

d) The COI gene must be variable enough that there are at least a few differences between each salmon species.

e) The COI gene must be conserved enough that the same PCR primers work for all the species being tested

The answers are: a), d), e).

Explanation:

Closely related species differ in their genetic sequence, that is, their DNA or deoxyribonucleic acid sequence to a small extent with variations or mutations like small insertion, deletion, substitution, etc. In order to distinguish between different species of organisms (salmon) it is necessary to compare the sequences of a gene which is mostly conserved through evolution. Cytochrome c oxidase I (COI) is a gene which has remained conserved through evolution showing slight variation in sequences in different species. The sequence of this COI gene can be compared among the different salmon species with a standard sequence of the COI gene, using several molecular techniques, for example PCR or polymerase chain reaction. However, this comparison includes certain restrictions or conditions: It is necessary that most of the sequence of the COI gene obtained from different salmon species is conserved or else no alignment with the standard sequence of the COI gene will be possible as no sequence match would be found. It is necessary that some amount of variation must exist in the COI gene sequence obtained from different species of salmon as otherwise no distinction can be made between the different species. It is necessary that the COI gene sequences obtained from different species of salmon must be conserved in those regions where the PCR primers bind as otherwise the primers would not be able to amplify the target region of the COI gene and the variation in the COI gene sequence in different salmon species cannot be studied.