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 Y, a gene duplication occurred in the lineage leading to A after it diverged from that, leading to B and C. Are genes AY1 and AY2 orthologous or paralogous? Are genes AY1 and BY orthologous or paralogous? Are genes BY and CY orthologous or paralogous? <>

Key Concepts

Orthologous Genes

Orthologous genes are genes in different species that evolved from a common ancestral gene through speciation. They typically retain the same function across species, making them crucial for understanding evolutionary relationships. In the context of the question, determining whether genes AY1 and BY are orthologous involves assessing if they originated from the same ancestral gene before the species diverged.

Paralogous Genes

Paralogous genes are genes that arise from a duplication event within a genome and evolve new functions over time. This means that while they share a common ancestor, they are found within the same species and can diverge in function. In the question, genes AY1 and AY2 are considered paralogous because they resulted from a duplication event after species A diverged from B and C.

Gene Duplication

Gene duplication is a process where a segment of DNA is copied, resulting in two identical or similar genes within the genome. This can lead to functional divergence, where one copy retains the original function while the other may evolve new functions. Understanding gene duplication is essential for analyzing the relationships between AY1, AY2, BY, and CY in the context of their evolutionary history.