Consider the phylogenetic trees below pertaining to three related species (A, B, C) that share a common ancestor (last common ancestor, or LCA). The lineage leading to species A diverges before the divergence of species B and C.

For gene Z, gene duplications have occurred in all species. Define orthology and paralogy relationships for the different Z genes. <>

Key Concepts

Orthology

Orthology refers to genes in different species that evolved from a common ancestral gene through speciation. These genes typically retain similar functions across species. In the context of species A, B, and C, the Z genes that are derived from the last common ancestor and are present in all three species would be considered orthologous.

Paralogy

Paralogy describes the relationship between genes that arise from duplication events within the same genome. These genes can evolve new functions over time. In the case of gene Z, if duplications occurred in species A, B, or C, the resulting Z genes would be classified as paralogous to each other, as they originated from a common ancestral gene within the same lineage.

Phylogenetic Trees

Phylogenetic trees are diagrams that represent the evolutionary relationships among various species based on their genetic information. They illustrate how species diverged from common ancestors over time. In this question, the phylogenetic tree helps visualize the divergence of species A, B, and C, providing context for understanding the orthology and paralogy of gene Z.