Just the facts #2
Okay, so, in response to elaine's question from two days ago, when she asked
"can you please tell me if there are cells that do not contain DNA? If yes, please give me some examples. Also if yes, what is the difference between DNA-less cells and cells with DNA as it what do they do differently and why do some have it and some don't (if it is known)."
The short answer is yes... and no.
In mammals, the red blood cells contain no nucleus or organelles, so contain no DNA. Red Blood cells are primarily for carrying oxygen throughout the body, and removing carbon dioxide from tissues, and are specialised for this function by having little in the way of cellular "baggage" in order to optimise their efficiency for the task. This also ensures the cell itself uses none of the oxygen it carries. This means they are incapable of self repair or cell division. Red blood cells are constructed in specialised regions of an animal body, for example, in the bone marrow, or in the liver in embryos. They may be stored to some extent in the spleen for periods when rapid physical activity requires larger volumes of oxygen to be delivered rapidly to muscle tissues.
Human Red Blood Cells
In plant tissues, the xylem cells, those carrying water and nutrients from the roots to other tissues, completely lack a protoplast at maturity. They also contain no DNA, but are effectively non-living tissues, and comprise the woody parts of plants. Again, this is to increase the efficiency of their primary function, that of conducting water through the plant. They are also incapable of self repair or cell division as a result.
Bacteria contain DNA, but unlike the linear chromosomes of multi-cellular organisms, it is arranged in a ring like structure. Certain organelles of plants, such as chloroplasts; and animals, such as mitochondria; contain their own DNA. Because such organelles are usually inherited directly form the female parent, and because their rate of mutation is very low, this allows certain genetic testing to gauge the rate of evolution between different species.
Bacteria
Viruses are complex organic entities, and though not classified as living, may also contain DNA, or in some cases RNA. They differ from living organisms in that they lack the ability to reproduce on their own, and require a host in order to multiply. Viral infections cause the most trouble to other organisms when they reduce the rate of cellular processes by hijacking the machinery and energy of a cell to make copies of the virus.
An "artificial" bacteriophage virus (electron micrograph)
"can you please tell me if there are cells that do not contain DNA? If yes, please give me some examples. Also if yes, what is the difference between DNA-less cells and cells with DNA as it what do they do differently and why do some have it and some don't (if it is known)."
The short answer is yes... and no.
In mammals, the red blood cells contain no nucleus or organelles, so contain no DNA. Red Blood cells are primarily for carrying oxygen throughout the body, and removing carbon dioxide from tissues, and are specialised for this function by having little in the way of cellular "baggage" in order to optimise their efficiency for the task. This also ensures the cell itself uses none of the oxygen it carries. This means they are incapable of self repair or cell division. Red blood cells are constructed in specialised regions of an animal body, for example, in the bone marrow, or in the liver in embryos. They may be stored to some extent in the spleen for periods when rapid physical activity requires larger volumes of oxygen to be delivered rapidly to muscle tissues.
Human Red Blood Cells
In plant tissues, the xylem cells, those carrying water and nutrients from the roots to other tissues, completely lack a protoplast at maturity. They also contain no DNA, but are effectively non-living tissues, and comprise the woody parts of plants. Again, this is to increase the efficiency of their primary function, that of conducting water through the plant. They are also incapable of self repair or cell division as a result.
Bacteria contain DNA, but unlike the linear chromosomes of multi-cellular organisms, it is arranged in a ring like structure. Certain organelles of plants, such as chloroplasts; and animals, such as mitochondria; contain their own DNA. Because such organelles are usually inherited directly form the female parent, and because their rate of mutation is very low, this allows certain genetic testing to gauge the rate of evolution between different species.
Bacteria
Viruses are complex organic entities, and though not classified as living, may also contain DNA, or in some cases RNA. They differ from living organisms in that they lack the ability to reproduce on their own, and require a host in order to multiply. Viral infections cause the most trouble to other organisms when they reduce the rate of cellular processes by hijacking the machinery and energy of a cell to make copies of the virus.
An "artificial" bacteriophage virus (electron micrograph)
posted by The Last Scientician at 10:34 AM
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