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Prokaryotic and eukaryotic DNA are the genetic blueprints found in all living organisms, but they have some key differences depending on the type of cell.
- Deoxyribonucleic acid (DNA) is the hereditary material present in all organisms.
- It contains the genetic code or specific information of an organism.
- Prokaryotic and eukaryotic DNA carry genetic information essential for their respective development, function, and reproduction.
- The chemical composition and structure of the DNA in both prokaryotic and eukaryotic cells are different.
- The main difference between prokaryotic and eukaryotic DNA is that prokaryotic DNA is found in the cytoplasm, whereas eukaryotic DNA is found in the cell's nucleus.
In this article, we will be discussing the major differences between prokaryotic and eukaryotic DNA.
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Key Terms: Differences between prokaryotic and eukaryotic DNA, Prokaryotic DNA, Eukaryotic DNA, Prokaryotic and eukaryotic cells, Genetic code
What is DNA?
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DNA, also known as deoxyribonucleic acid, is one of the most essential parts of an organism.
- It contains the hereditary unit of an organism.
- The DNA contains information about the organism as the genetic code.
- This information is required for an organism to develop.
- The DNA has a structure with double helix strands which are anti-parallel and remain coiled around each other.
- These structures contain the genetic information that is transmitted to RNA through a process known as transcription.
DNA
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What is Prokaryotic DNA?
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Prokaryotic DNA refers to the genetic material found in prokaryotic cells, such as bacteria.
- This DNA is located in the cytoplasm, a region called the nucleoid and is not enclosed by a nuclear membrane.
- Unlike eukaryotes, prokaryotes have a single, circular chromosome that contains all their genetic information.
- Proteins associated with the nucleoid help condense and organize the prokaryotic chromosome into loops within the nucleoid region.
Prokaryotic DNA
What is Eukaryotic DNA?
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Eukaryotic DNA refers to the genetic material found in eukaryotic cells, such as animals and plants.
- It is located within a membrane-bound organelle called the nucleus.
- Most of the eukaryotic DNA resides in the nucleus.
- Some DNA is also found in organelles like mitochondria and chloroplasts.
- Eukaryotic DNA is made up of the same basic building blocks (adenine, thymine, guanine, and cytosine) as prokaryotic DNA.
- It consists of multiple linear chromosomes, each containing long strands of DNA tightly coiled around proteins called histones.
- This tight coiling and dense packing allow the large amount of DNA in eukaryotes to fit within the nucleus.
Difference Between Prokaryotic DNA and Eukaryotic DNA
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The differences between prokaryotic and eukaryotic DNA are:
| Parameters | Prokaryotic DNA | Eukaryotic DNA |
|---|---|---|
| Location | It is found freely in the central portion of the cytoplasm. | It is found within the nucleus. |
| Size | The size of DNA in a prokaryote is usually less than 0.1 pg. | The size of DNA in eukaryotes is high, usually more than 1 pg. |
| Chromosome | These do not form chromosomes. | They form chromosomes in the nucleus. |
| Number of Chromosomes | The prokaryotic DNA is organized into a single chromosome. | The eukaryotic DNA is organized into many chromosomes. |
| Occurrence | Is found occurring as a closed covalent circular form of DNA. | Occurs as a linear form of DNA with two ends. |
| Introns | Introns are absent in the coding region of prokaryotic DNA. | Introns are present in the coding region of eukaryotic DNA. |
| Nucleosome | There is no formation of nucleosomes in prokaryotic DNA. | Nucleosomes are formed in the DNA of eukaryotic cells. |
| Genomes | The genome of prokaryotes is too small and contains a few genes ranging from several kb to MB in size. | The eukaryotic genome is usually larger contains a few thousand genes (~21,000 genes in humans) and is made up of billions of base pairs. |
| Quantity of the DNA | The quantity of the DNA is less as compared to that in eukaryotes. | The quantity of the DNA is more. |
| DNA Replication | DNA Replication occurs in the cytoplasm of the cell. | DNA Replication is found occurring in the nucleus of the cell. |
| Transposons | The prokaryotic DNA does not consist of transposons. | The eukaryotic DNA consists of transposons. |
| Histone Proteins | This DNA does not interact or associate with histone proteins. | They interact with histone proteins. |
| Plasmid DNA | Prokaryotes possess a smaller, circular, single-stranded DNA, known as the plasmid DNA. | Eukaryotes do not possess plasmid DNA. |
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| Related Concepts | ||
|---|---|---|
| Structure of DNA | Structure of RNA | Cell Biology |
| Plasma Membrane | What are the 22 Bones of the Skull? | Plant cell |
Things to Remember
- DNA is one of the most essential parts of an organism, containing the hereditary unit of an organism.
- In eukaryotic cells, the cytoplasm contains nucleus and cell organelles and the amount of DNA is also greater.
- The prokaryotic cells do not have a nucleus, nor cell organelles and contain very little amount of DNA.
- There is no formation of nucleosomes in prokaryotic DNA, while nucleosomes are formed in the DNA of eukaryotic cells.
- Introns are absent in the coding region of prokaryotic DNA but they are present in the coding region of eukaryotic DNA.
- The prokaryotic chromosome is circular and does not fold with histone protein because it does not have to fit inside the nucleus.
- The eukaryotic chromosome is linear and it must be fitted in the nucleus of a cell.
Sample Questions
Ques: What does ‘S’ refer to in a 70S and an 80S ribosome? (1 Mark)
Ans: 'S' in a 70 S and 80 S ribosome refers to Svedberg’s Unit or sedimentation coefficient
Ques: How is the structure of eukaryotic DNA different from prokaryotic DNA? (1 Mark)
Ans: The prokaryotic DNA is found occurring as a closed covalent circular form of DNA whereas, the eukaryotic DNA occurs as a linear form of DNA with two ends.
Ques: Define cell theory. (2 Marks)
Ans: The main points of the Cell Theory as proposed by Schlieden and Schwann are:
- All cells seem to have the same basic chemical structure.
- All living organisms are made up of one or more cells on Earth.
- The cell is the basic structural and functional unit of life.
- New cells are formed from pre-existing cells.
- Hereditary information is passed from the parent cell to the child cell.
- The fundamental biochemical reactions of life take place within the cell itself.
Ques: What is the difference between Prokaryotic and Eukaryotic cells? (5 Marks)
Ans: The two main types of cells are - Prokaryotic cells and Eukaryotic cells. This difference between them is based on the presence of the nucleus. A eukaryotic cell has a nucleus but a prokaryotic cell does not have a nucleus.
The differences between prokaryotic and eukaryotic cells are as follows-
| Prokaryotic cell | Eukaryotic cell |
|---|---|
| It is a single-membrane system. | It is a double membrane system. |
| There are no streaming movements of the cytoplasm. | The cytoplasm shows streaming movements. |
| Ribosomes are of 70 S type. | Ribosomes are of 80 S type. |
| There are no occurrences of endocytosis or exocytosis. | Endocytosis and exocytosis occur. |
| The cytoplasm in these cells lacks cell organelles. | The cytoplasm in these cells contains various cell organelles. |
| Sexual reproduction is absent but parasexuality (reproduction method of single-celled organisms or fungi in the absence of meiosis) is present. | Sexual reproduction is present. |
Ques: State the characteristics of prokaryotic cells. (3 Marks)
Ans: The following are the characteristics of prokaryotic cells
- The prokaryotic cells do not have membrane-bound organelles.
- It has only one membrane.
- The cytoplasm has dense granules mostly ribosomes.
- Mitochondria, nucleus, and chloroplast are absent.
- The DNA is circular and not associated with basic proteins.
- The ribosomes are of 70 S type.
Ques: What is prokaryotic DNA? (1 Mark)
Ans: Prokaryotic DNA is a single, circular molecule located in a region of the cytoplasm called the nucleoid. Unlike eukaryotes, the nucleoid is not enclosed by a nuclear membrane.
Ques: Does prokaryotic DNA have introns? (1 Mark)
Ans: Prokaryotic DNA does not consist of introns. They have transcription linked with translation. Therefore, there is no space for intron splicing since intron splicing stops the coupling.
Ques: What are polyribosomes? (2 Marks)
Ans: A group of ribosomes that are bound to an mRNA molecule like beads attached to a thread is called a polyribosome. The mRNA in prokaryotes is polycistronic i.e. containing more than one protein and thus, it forms the site for protein synthesis and also translates mRNA instructions into polypeptides.
Ques: Eukaryotic cells have organelles that may
1. not be bound by a membrane
2. bound by a single membrane
3. bound by a double membrane
Group the various subcellular organelles into these three categories. (2 Marks)
Ans: 1. Non-membrane bound cell organelles: Ribosome, Centrosome, Nucleolus, Cytoskeletal structures.
- Single membrane-bound cell organelles: ER, GB, Lysosome, Vacuoles, Microbodies (Glyoxysomes and Peroxisomes), Thylakoid.
- Double membrane-bound cell organelles: Plastid, Mitochondria, and Nucleus.
Ques: What are histones? What are their functions? (3 Marks)
Ans: In eukaryotes, there are positively charged, basic proteins named histones. Histones are rich in the basic amino acid residues of lysines and arginines. Both the amino acid residues carry positive charges in their side chains. Histones are organized to form a unit of eight molecules known as histone octamer. The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called a nucleosome. A typical nucleosome contains 200 bp of DNA helix.
Ques: What is the difference between prokaryotic and eukaryotic DNA? (3 Marks)
Ans: The differences between prokaryotic and eukaryotic DNA are -
| Prokaryotic DNA | Eukaryotic DNA |
|---|---|
| Prokaryotic DNA does not form chromosomes. It is found freely in the central portion of the cytoplasm. | Eukaryotic DNA forms chromosomes in the nucleus. |
| As compared to eukaryotes, the quantity of the DNA is less. | The quantity of the DNA is more. |
| It is found freely in the central portion of the cytoplasm. | It is found within the nucleus. |
| This DNA does not interact or associate with histone proteins. | They interact with histone proteins. |
| DNA Replication occurs in the cytoplasm of the cell. | DNA Replication is found occurring in the nucleus of the cell. |
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