Question

As described in Chapter 4 (refer back to Table 4.1), actin is a protein that is a component of the cytoskeleton found in eukaryotic cells. If you compared the sequence of an actin gene in bald eagles with that in other species, which of the following species would you expect to have an actin gene sequence most similar to the eagle’s? a. human b. sea bass c. baker’s yeast d. sparrow e. salamander

Short answer

The sparrow would be expected to have an actin gene sequence most similar to the bald eagle's.

Step-by-step solution

Understand the species classification

Bald eagles and sparrows belong to the class Aves (birds). Humans are in class Mammalia, sea bass in class Actinopterygii (ray-finned fishes), bakers yeast is a Fungi, and the salamander is in class Amphibia. An understanding of the taxonomy suggests that the species most likely to have a similar actin gene sequence with the bald eagle from the provided list would be another bird, in this case the sparrow.

Compare with other species

Based on the classification of the species, it's clear that the sparrow, another bird species, would likely have the actin gene sequence most similar to the bald eagle. Although the other species, such as the human or the sea bass, might have similar actin genes (because actin is a highly conserved protein), the one most similar to the bald eagle would be from a species in the same class.

Key concepts

Species Classification

Understanding the classification of species is essential in biology and serves as the foundation for predicting gene sequence similarity. The discipline of taxonomy organizes living organisms into hierarchical categories based on shared characteristics and evolutionary relationships.

For instance, within the animal kingdom, organisms are classified into phyla, then further divided into classes, orders, families, genera, and species. Birds, such as bald eagles and sparrows, are classified under the class Aves. This classification indicates that they share a common ancestor and have evolved similar traits, including aspects of their genetic makeup. Consequently, when comparing the actin gene sequence of a bald eagle, it is logical to postulate that the most similar sequence would be found in closely related species within the same class, such as the sparrow.

In contrast, organisms like humans, sea bass, and salamanders belong to different classes and thus have more distant common ancestors with birds. Baker's yeast, being a fungus, is even further removed in the tree of life. While some genes are conserved across many forms of life, the actin gene sequence will most closely resemble that of organisms within the same classification group.

Eukaryotic Cytoskeleton

The eukaryotic cytoskeleton is a complex network of fibrous proteins that provide structural support, shape, and motility to eukaryotic cells. It is composed of three main elements: microfilaments, intermediate filaments, and microtubules.

Actin is a globular protein that polymerizes to form microfilaments, which are involved in various cellular processes such as muscle contraction, cell division, and cell signaling. As an integral part of the cytoskeleton, actin proteins are vital for maintaining cell integrity and facilitating cellular movement.

Given its fundamental role across eukaryotic species, the genes encoding actin proteins are highly conserved throughout evolution. However, there are variations in the actin gene sequence between different species that reflect their evolutionary divergence. Thus, comparing actin gene sequences is one approach to study the evolutionary relatedness and functional similarities among diverse eukaryotic organisms.

Gene Sequence Similarity

Gene sequence similarity is a crucial concept in genetics that underlies the understanding of evolutionary relationships between species. The degree of similarity in the nucleotide sequences of a gene can provide insights into how closely related two species are.

Genes that perform fundamental cellular functions, like those for actin, tend to be highly conserved; meaning, they undergo fewer changes over time because mutations in these genes could result in detrimental effects on the organism. Despite this conservation, some variations between species do occur, which helps scientists trace the evolutionary history and lineage.

By comparing the sequences of these conserved genes across different species, researchers can construct phylogenetic trees that visually represent the evolutionary pathways. Assessing gene sequence similarity is not only vital for understanding evolutionary biology but also has practical applications in fields like medicine, where it may help in identifying potential gene targets for treatment or understanding the origins of genetic diseases.