Name three characteristics of mitochondria and chloroplasts that support the endosymbiotic hypothesis of eukaryotic evolution?

Mitochondria & Chloroplasts:

1. Have their own DNA

2. Have DNA more like a prokaryote’s than a eukaryote’s

2a. Chromosome is circular, not linear

2b. No histones

3. Can replicate independently of the cell

4. Divide by binary fission, not mitosis

5. Have double membranes

6. Have associated with their inner membrane enzymes & transport systems homologous to those of prokaryotes

7. Have ribosomes more like a prokaryote’s than a eukaryote’s

7a. Smaller size (70S, like prokaryote, instead of 80S)

7b. Nucleotide sequence closer to that of prokaryotes

8. 1st amino acid formylmethionine (eukaryotes use methionine)

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Sra

Three characteristics of mitochondria and chloroplasts that support the endosymbiotic hypothesis of eukaryotic evolution are:

1. Double Membrane: Both mitochondria and chloroplasts have double membranes. The outer membrane is derived from the host cell's plasma membrane, while the inner membrane is believed to be derived from the plasma membrane of the engulfed prokaryote. This suggests that these organelles were once free-living prokaryotic cells that were engulfed by a host cell.

2. DNA: Mitochondria and chloroplasts have their own DNA separate from the nuclear DNA of the host cell. This DNA is circular, similar to bacterial DNA, and contains genes necessary for the organelles' function. This provides evidence that these organelles were once independent prokaryotes.

3. Replication: Mitochondria and chloroplasts have the ability to replicate themselves within the host cell. They have their own machinery and enzymes to replicate their DNA and divide similar to bacteria. This supports the idea that they were once free-living organisms capable of self-replication.

The endosymbiotic hypothesis proposes that mitochondria and chloroplasts were once free-living bacteria that were engulfed by ancestral eukaryotic cells and eventually developed a symbiotic relationship. There are several characteristics of mitochondria and chloroplasts that support this hypothesis:

1. Double Membrane Structure: Both mitochondria and chloroplasts have a double membrane structure. The outer membrane is similar to the host cell's membrane, while the inner membrane contains unique proteins. This can be explained by the engulfment of the bacteria by the host cell, with the outer membrane derived from the host cell's membrane and the inner membrane derived from the engulfed bacterium's membrane.

To observe this characteristic, you can use electron microscopy to examine the structure of mitochondria or chloroplasts. This can be done either by studying images of these organelles or by performing experiments in a laboratory, isolating and studying these organelles through techniques like cell fractionation.

2. Presence of Circular DNA: Mitochondria and chloroplasts have their own circular DNA molecules, similar to bacterial DNA. This circular DNA encodes essential genes necessary for their function. This is consistent with the idea that mitochondria and chloroplasts were once independent bacteria that contained their own genetic material.

To determine if mitochondria or chloroplasts possess circular DNA, you can perform DNA extraction techniques followed by DNA analysis methods such as PCR or gel electrophoresis. By comparing the DNA extracted from these organelles to the nuclear DNA of the host cell, you can observe differences in the structure and content of the genomes.

3. Replication and Division: Mitochondria and chloroplasts replicate and divide independently within the eukaryotic cell. This ability to self-replicate, similar to free-living bacteria, supports the endosymbiotic hypothesis. Mitochondria and chloroplasts replicate their own DNA and divide through a process similar to binary fission, which is characteristic of bacterial reproduction.

To observe replication and division of mitochondria or chloroplasts, you can employ techniques such as time-lapse microscopy to monitor the organelles in living cells or perform immunofluorescence staining to visualize specific markers associated with replication and division.

By examining these characteristics, scientists have obtained supporting evidence for the endosymbiotic hypothesis. However, it is important to note that this hypothesis is continually tested and refined as more research is conducted in the field of evolutionary biology.