You want to make a phylogenetic tree of a group of three related species of lizards that live on an island. Their genome sequences are highly similar except for a gene that controls body size. In that region of the genome, one of the lizard species has one copy of the growth control gene (L1), the second species has a duplication of the growth control gene (L2) and the third species has three copies of the same gene (L3). The lizard species show an increase in size depending on how many copies of the growth control gene they have (L1 is smallest, L2 is medium-sized and L3 is largest). Is this enough information to determine the phylogenetic relationships between the species, and predict which of the species arrived on the island first (and is the ancestral species)? Yes, because the ancestral lizard genome probably had a single copy of the growth control gene and after arriving on the island it was duplicated, resulting in species L2, and then another duplication occurred resulting in species L3. So, there were two changes, with increasing genome complexity over time. No, because each of the possibilities involves two changes to the growth control genes, so there would be no way to determine which tree was the accurate one. Therefore, additional evidence would have to be considered, such as lifestyle, body morphology, and an example of an outgroup species of the most closely related lizard that does not live on this island. Yes, because there could have been two copies of the growth control gene in the ancestral lizard originally (species L2), and then species L1 lost a copy by deletion, and species L3 gained a copy by duplication. So, there were two changes, one an evolutionary reversal, the other an evolutionary addition. No, because the ancestral species could have had three copies of the gene (species L3), and then upon arrival at the island, lost one gene, resulting in species L2, and then L2 could have lost another copy of the gene, resulting in L1.
You want to make a phylogenetic tree of a group of three related species of lizards that live on an island. Their genome sequences are highly similar except for a gene that controls body size. In that region of the genome, one of the lizard species has one copy of the growth control gene (L1), the second species has a duplication of the growth control gene (L2) and the third species has three copies of the same gene (L3). The lizard species show an increase in size depending on how many copies of the growth control gene they have (L1 is smallest, L2 is medium-sized and L3 is largest). Is this enough information to determine the phylogenetic relationships between the species, and predict which of the species arrived on the island first (and is the ancestral species)?
Yes, because the ancestral lizard genome probably had a single copy of the growth control gene and after arriving on the island it was duplicated, resulting in species L2, and then another duplication occurred resulting in species L3. So, there were two changes, with increasing genome complexity over time.
No, because each of the possibilities involves two changes to the growth control genes, so there would be no way to determine which tree was the accurate one. Therefore, additional evidence would have to be considered, such as lifestyle, body morphology, and an example of an outgroup species of the most closely related lizard that does not live on this island.
Yes, because there could have been two copies of the growth control gene in the ancestral lizard originally (species L2), and then species L1 lost a copy by deletion, and species L3 gained a copy by duplication. So, there were two changes, one an evolutionary reversal, the other an evolutionary addition.
No, because the ancestral species could have had three copies of the gene (species L3), and then upon arrival at the island, lost one gene, resulting in species L2, and then L2 could have lost another copy of the gene, resulting in L1.
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