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Ch. 7 - Inside the Cell
All textbooksFreeman 8th EditionCh. 7 - Inside the CellProblem 7
Chapter 7, Problem 7

Why was finding a close relationship between mitochondrial DNA and bacterial DNA considered particularly strong evidence in favor of the endosymbiosis theory?

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Identify the key components: Understand that mitochondrial DNA is similar to bacterial DNA, and the endosymbiosis theory suggests that mitochondria originated from bacteria that entered into a symbiotic relationship with early eukaryotic cells.
Examine the evidence: Recognize that the close relationship between mitochondrial DNA and bacterial DNA suggests that mitochondria were once free-living bacteria that were absorbed by another cell.
Understand the implications: This DNA similarity supports the idea that mitochondria retain some characteristics of their bacterial ancestors, including their own DNA, which is separate from the nuclear DNA of the eukaryotic cell.
Consider the uniqueness: Note that mitochondria, like bacteria, can replicate independently of the cell in which they reside, further supporting the endosymbiosis theory.
Reflect on the broader impact: Realize that this evidence helps explain the evolution of complex cells (eukaryotes) from simpler ones (prokaryotes), fundamentally shaping our understanding of cellular and evolutionary biology.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Endosymbiosis Theory

The endosymbiosis theory posits that eukaryotic cells originated through a symbiotic relationship between early ancestral prokaryotic cells. This theory suggests that certain organelles, particularly mitochondria and chloroplasts, were once free-living bacteria that were engulfed by a host cell, leading to a mutually beneficial relationship. The evidence supporting this theory includes similarities in DNA, ribosomes, and reproduction between these organelles and bacteria.
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Mitochondrial DNA

Mitochondrial DNA (mtDNA) is the genetic material found in mitochondria, the energy-producing organelles in eukaryotic cells. Unlike nuclear DNA, mtDNA is inherited maternally and is circular in structure, similar to bacterial DNA. The close relationship between mtDNA and bacterial DNA supports the idea that mitochondria originated from a prokaryotic ancestor, reinforcing the endosymbiosis theory.
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Comparative Genomics

Comparative genomics is the field of study that involves comparing the genomic features of different organisms to understand their evolutionary relationships. By analyzing similarities and differences in DNA sequences, researchers can infer how species are related and trace the evolutionary history of genes and organelles. The close genetic relationship between mitochondrial DNA and bacterial DNA provides compelling evidence for the evolutionary link proposed by the endosymbiosis theory.
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Related Practice
Textbook Question

Cells that line your intestines are known to possess a large number of membrane proteins that transport small molecules and ions across the plasma membrane. Which of the following cell structures would you expect to be required for this characteristic of the cells? a. the endoplasmic reticulum b. peroxisomes c. lysosomes d. the cell wall

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Textbook Question

Consider the endosymbiosis theory for the origin of the mitochondrion. How did each endosymbiotic partner benefit from the relationship?

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Textbook Question

Most of the proteins that enter the nucleus possess a nuclear localization signal (NLS), even if they are small enough to pass through the nuclear pore complex unhindered. Why would a small protein have an NLS, when it naturally diffuses across the nuclear pore complex without one?

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Textbook Question

The eukaryotic cytoskeleton is a highly dynamic network of filaments and motor proteins. Which of the following correctly describe activities of these cytoskeletal components? Select True or False for each statement. T/F Myosin motors walk toward the plus ends of intermediate filaments. T/F Dynein motors are responsible for the whip-like movement of eukaryotic flagella. T/F Kinesin motors move vesicles along tracks toward the microtubule-organizing center. T/F Actin filaments are required for cytoplasmic streaming.

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Textbook Question

When analyzing a sample of cells from a patient, you find the lysosomes are filled with undigested material. This observation makes you think that the lysosomes are not functioning properly. What are three different defects that could be responsible for malfunctioning lysosomes?

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Textbook Question

George Palade's research group used the pulse–chase assay to elucidate the secretory pathway in pancreatic cells. If they had instead performed this assay on muscle cells, where would you expect the labeled proteins to end up during the chase? (Muscle cells consist primarily of actin and myosin filaments and have high energy demands for muscle contraction.)

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