Which are typical molecular sources used in inferring phylogenetic relationships?

Which are typical molecular sources used in inferring phylogenetic relationships?

• A. Chloroplast SSRs and tRNA genes.
• B. Nuclear introns only.
• C. Mitochondrial DNA, ribosomal RNA, and conserved proteins.
• D. Mitochondrial DNA only.

Answer: (C)

Inferring evolutionary relationships relies on comparing homologous genetic sequences that come from common ancestors. Mitochondrial DNA, ribosomal RNA genes, and conserved proteins are common sources because they provide complementary information across different timescales. Mitochondrial DNA evolves relatively quickly in many animals, is present in many copies per cell, and usually doesn’t recombine, which makes it easy to sequence and particularly useful for resolving recent divergences and species-level relationships. However, because it is inherited maternally, it only traces the maternal lineage and can be misleading if there has been introgression or lineage sorting, so it’s best used together with other data. Ribosomal RNA genes, such as 16S or 18S/28S, are highly conserved across broad groups, allowing alignments across distant taxa. Their conserved regions enable comparisons across deep evolutionary distances, while the more variable parts provide signal at intermediate levels. They serve as a backbone for broad, cross-tpecies phylogenies. Conserved proteins—genes essential for basic cellular functions that exist across many lineages—offer another reliable signal. They tend to evolve slowly enough to be comparable across diverse taxa and help place very distant lineages, providing a check against patterns seen in mtDNA and rRNA data. Using these sources together balances rate differences and biases, yielding a more robust evolutionary picture. Other options tend to be more specialized, problematic for broad phylogenies, or incomplete if used alone.

Inferring evolutionary relationships relies on comparing homologous genetic sequences that come from common ancestors. Mitochondrial DNA, ribosomal RNA genes, and conserved proteins are common sources because they provide complementary information across different timescales. Mitochondrial DNA evolves relatively quickly in many animals, is present in many copies per cell, and usually doesn’t recombine, which makes it easy to sequence and particularly useful for resolving recent divergences and species-level relationships. However, because it is inherited maternally, it only traces the maternal lineage and can be misleading if there has been introgression or lineage sorting, so it’s best used together with other data.

Ribosomal RNA genes, such as 16S or 18S/28S, are highly conserved across broad groups, allowing alignments across distant taxa. Their conserved regions enable comparisons across deep evolutionary distances, while the more variable parts provide signal at intermediate levels. They serve as a backbone for broad, cross-tpecies phylogenies.

Conserved proteins—genes essential for basic cellular functions that exist across many lineages—offer another reliable signal. They tend to evolve slowly enough to be comparable across diverse taxa and help place very distant lineages, providing a check against patterns seen in mtDNA and rRNA data.

Using these sources together balances rate differences and biases, yielding a more robust evolutionary picture. Other options tend to be more specialized, problematic for broad phylogenies, or incomplete if used alone.