Genes related through vertical descent from a common ancestral gene are called
1. heterologous
2. xenologous
3. paralogous
4. orthologous

Detailed Explanation:
Correct Answer:
4. Orthologous

What Are Orthologous Genes?

Orthologous genes are genes in different species that originated from a common ancestral gene through vertical descent. These genes typically retain the same function across different species. For example, the human gene for hemoglobin and the gene for hemoglobin in mice are orthologous because they both descended from a common ancestral gene and generally have the same function of oxygen transport.

Types of Gene Relationships:

1. Orthologous Genes (Correct Answer)
   These genes are related by common ancestry due to speciation events. The key aspect of orthologous genes is that they diverge after the species split but often maintain similar functions. For example, the hemoglobin gene in humans and the same gene in chimpanzees are orthologs. They came from a common ancestor before humans and chimps diverged from each other evolutionarily.

2. Paralogous Genes
   Paralogous genes are genes that arise by duplication within the same genome. Over time, they may acquire different functions. These genes are related by descent, but not necessarily by common function. For example, different globin genes in humans (e.g., alpha-globin and beta-globin) are paralogous because they evolved from a common ancestral gene through duplication within the same species.

3. Heterologous Genes
   The term heterologous refers to genes that are different or not related in a typical evolutionary sense. In molecular biology, it is sometimes used to describe genes that come from unrelated species or have functions that are different from one another.

4. Xenologous Genes
   Xenologous genes are genes that are transferred between species by horizontal gene transfer (not vertical descent). These genes are not inherited from a common ancestor but are transferred from one organism to another, usually through processes like bacterial conjugation or viral infection.

Summary of Key Terms:

• Orthologous Genes: Same function, different species, vertical descent (correct).

• Paralogous Genes: Same species, duplication event, may have different functions.

• Heterologous Genes: Genes that are not related or do not share common ancestry.

• Xenologous Genes: Genes transferred between species through horizontal gene transfer.

Conclusion:

Genes related through vertical descent from a common ancestral gene are called orthologous genes. Understanding gene relationships is important for evolutionary biology, helping us trace the functions and origins of genes across species and how they evolve over time.