Which one of the following cell organelles contains DNA?
Mitochondrion
Understanding Cell Organelles and DNA Content
Cell organelles are specialized structures within a cell that perform specific functions. The genetic material, DNA, is primarily found in the nucleus of eukaryotic cells. However, certain organelles also contain their own DNA, which is separate from the nuclear DNA. This question asks which of the given cell organelles contains DNA.
Analyzing the Options for DNA Content
Let's examine each of the provided cell organelles to determine if they contain DNA:
- Golgi apparatus: The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles. It is a membrane-bound organelle but does not contain its own genetic material (DNA).
- Mitochondrion: Mitochondria are often called the "powerhouses" of the cell because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. Mitochondria are unique among the listed organelles because they contain their own circular DNA molecule, known as mitochondrial DNA (mtDNA). This mtDNA carries genes essential for some mitochondrial functions.
- Lysosome: Lysosomes are membrane-bound organelles containing digestive enzymes. They are involved in breaking down waste materials and cellular debris. Lysosomes do not contain DNA.
- Endoplasmic reticulum: The endoplasmic reticulum (ER) is a network of membranes found throughout the cytoplasm of eukaryotic cells, involved in protein and lipid synthesis and transport. The ER does not contain DNA.
Identifying the Organelle with DNA
Based on the analysis of each option, the mitochondrion is the only organelle among the choices that contains its own DNA.
| Cell Organelle | Contains DNA? | Primary Function |
|---|---|---|
| Golgi apparatus | No | Protein/lipid modification, sorting, packaging |
| Mitochondrion | Yes | ATP production (cellular respiration) |
| Lysosome | No | Waste breakdown, digestion |
| Endoplasmic reticulum | No | Protein/lipid synthesis and transport |
Conclusion on Organelles Containing DNA
The question asks which one of the listed cell organelles contains DNA. As discussed, the mitochondrion possesses its own distinct DNA molecule. Therefore, the mitochondrion is the correct answer.
Revision Table: Key Cell Organelles and DNA
| Organelle | DNA Present? | Notes |
|---|---|---|
| Nucleus | Yes | Main location of genomic DNA in eukaryotes |
| Mitochondrion | Yes | Contains circular mitochondrial DNA (mtDNA) |
| Chloroplast (in plants/algae) | Yes | Contains circular chloroplast DNA (cpDNA) |
| Golgi apparatus | No | Part of endomembrane system, no DNA |
| Lysosome | No | Part of endomembrane system, no DNA |
| Endoplasmic reticulum | No | Part of endomembrane system, no DNA |
| Ribosomes | No | Involved in protein synthesis, made of RNA and protein |
Additional Information: Mitochondrial DNA Significance
The presence of DNA in mitochondria (and chloroplasts in plant cells) is significant and supports the endosymbiotic theory. This theory suggests that mitochondria and chloroplasts originated from ancient prokaryotic organisms that were engulfed by early eukaryotic cells. The fact that mitochondria have their own DNA, ribosomes, and can replicate somewhat independently of the cell cycle provides evidence for this theory.
Mitochondrial DNA is typically a small, circular molecule that codes for a limited number of proteins, mostly components of the electron transport chain involved in ATP production, and also some ribosomal RNAs and transfer RNAs needed for protein synthesis within the mitochondrion. Because it has its own genetic system, the mitochondrion is sometimes referred to as a semi-autonomous organelle.
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