Question

Why do scientists believe DNA found in mitochondria and chloroplasts similar to that of prokaryotes? They have lot of energy in them that only eukaryotes have. They were once independent prokaryotes that were engulfed by a larger host. Scientists do not believe that DNA in these organelles are similar to prokaryotes.

Answer 1

Scientists believe that the DNA found in mitochondria and chloroplasts is similar to that of prokaryotes due to several key pieces of evidence supporting the endosymbiotic theory. This theory posits that these organelles originated as free-living prokaryotic cells that were engulfed by a larger ancestral eukaryotic cell. Here are the main reasons for this belief:

1. Genetic Similarity: The DNA in mitochondria and chloroplasts is circular and resembles the DNA found in prokaryotes (specifically, bacteria). In contrast, the DNA in the nucleus of eukaryotic cells is linear and organized into chromosomes. This circular form is a characteristic typical of prokaryotic genomes.

2. Structural Similarities: Mitochondria and chloroplasts have double membranes and other structural features that are similar to those of certain bacteria. This includes the presence of their own ribosomes that are more similar to bacterial ribosomes than to eukaryotic ribosomes.

3. Replication: Mitochondria and chloroplasts reproduce through a process similar to binary fission, which is how prokaryotic cells divide. This is different from the mitotic division seen in the nucleus of eukaryotic cells.

4. Functional Evidence: The functions performed by mitochondria and chloroplasts are similar to those of prokaryotic organisms. For example, mitochondria are involved in cellular respiration, a process that is akin to processes found in certain aerobic bacteria. Similarly, chloroplasts perform photosynthesis, which is also a function seen in some prokaryotic organisms, like cyanobacteria.

5. Endosymbiotic Relationship: The endosymbiotic theory explains that the relationships between these organelles and eukaryotic cells are mutually beneficial. Over time, the engulfed prokaryotes evolved into essential organelles, leading to the complexity observed in eukaryotic life.

These lines of evidence collectively support the idea that mitochondria and chloroplasts are more closely related to prokaryotes than to the eukaryotic cells that contain them, validating the endosymbiotic theory. So, in summary, scientists do indeed believe that the DNA in mitochondria and chloroplasts is similar to that of prokaryotes, based on multiple forms of evidence reinforcing the theory of their evolutionary origins.

Answer 2

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Answer 3

Scientists believe that the DNA found in mitochondria and chloroplasts is similar to that of prokaryotes because of the genetic similarity. The DNA in these organelles is circular and shares structural and sequence features with prokaryotic DNA, supporting the idea that mitochondria and chloroplasts originated from free-living prokaryotes that were engulfed by ancestral eukaryotic cells, as proposed by the endosymbiotic theory.