why do eukaryotic cells have more dna than they need?
439585
In many cases the so-called 'junk' DNA carried by many organisms is probably similar to the old wives' tale that we only use 10% of our brains.\n\nIt looks like a lot of DNA goes unused in the day to day operations of the cell and in the process of gene transcription, but this probably means we just don't know yet what it does, and not that it isn't needed.\n\nEverytime medical science has said that some organ or other is vestigial and serves no purpose, we soon find out that it really does have a function.  Not always a major role, or a vital function, but some function.  Usually this occurs sometime after the doctors have spent decades performing needless operations removing tonsils or appendixes willy nilly.\n\nIt seems likely that someday we'll find that a lot of that DNA really does serve a purpose.  Perhaps it is only switched on in special circumstances, or maybe it's something like a glossary that reminds the cell how the stuff in the rest of the DNA is supposed to be spelled, so that random errors can be corrected (or added to).  \n\nMaybe it really is useless, ancient data.  The genetic equivalent of our high school yearbooks or the address book from twenty years ago that's still stuck in the back of one desk drawer.  \n\nPerhaps it's material that the cell isn't using right now, but would be really valuable if we did.  Maybe it's like that cardboard box that goes through six moves without being opened, and so we finally open it, and HEY, COOL!!! LEGO!!!!
767384
Most of the cells in your body are identical in terms of genetic content (DNA/chromosomes).\n\nThe huge variety of cells is due to the fact that as we develop from a fertilized egg into an embryo and beyond, there are different signals passed around constantly that direct cells to divide and grow in certain ways such that a human being is the end result.  Throughout life, these "molecular instructions" are maintained so that our cells stay the proper type.  (Sometimes, improper maintenance of these directions can lead to cancer.)\n\nExpression of genes (that is, transcription from DNA to mRNA, and then translation to protein) will of course dictate how the process goes.  Different proteins exist in each different cell type due to variable expression.
1136356
Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. DNA is a long polymer of nucleotides (a polynucleotide) and encodes the sequence of the amino acid residues in proteins using the genetic code, a triplet code of nucleotides.\nIn complex eukaryotic cells such as those from plants, animals, fungi and protists, most of the DNA is located in the cell nucleus. By contrast, in simpler cells called prokaryotes, including the eubacteria and archaea, DNA is not separated from the cytoplasm by a nuclear envelope. The cellular organelles known as chloroplasts and mitochondria also carry DNA.\nDNA is often referred to as the molecule of heredity as it is responsible for the genetic propagation of most inherited traits. In humans, these traits can range from hair colour to disease susceptibility. During cell division, DNA is replicated and can be transmitted to offspring during reproduction. Lineage studies can be done based on the facts that the mitochondrial DNA only comes from the mother, and the male Y chromosome only comes from the father.\nEvery person's DNA, their genome, is inherited from both parents. The mother's mitochondrial DNA together with twenty-three chromosomes from each parent combine to form the genome of a zygote, the fertilized egg. As a result, with certain exceptions such as red blood cells, most human cells contain 23 pairs of chromosomes, together with mitochondrial DNA inherited from the mother.\n\nMolecular structure:\nAlthough sometimes called "the molecule of heredity", DNA macromolecules as people typically think of them are not single molecules. Rather, they are pairs of molecules, which entwine like vines to form a double helix (see the illustration at the right).\nEach vine-like molecule is a strand of DNA: a chemically linked chain of nucleotides, each of which consists of a sugar (deoxyribose), a phosphate and one of five kinds of nucleobases ("bases"). Because DNA strands are composed of these nucleotide subunits, they are polymers.\nThe diversity of the bases means that there are five kinds of nucleotides, which are commonly referred to by the identity of their bases. These are adenine (A), thymine (T), uracil (U), cytosine (C), and guanine (G). U is rarely found in DNA except as a result of chemical degradation of C, but in some viruses, notably PBS1 phage DNA, U completely replaces the usual T in its DNA. Similarly, RNA usually contains U in place of T, but in certain RNAs such as transfer RNA, T is always found in some positions. Thus, the only true difference between DNA and RNA is the sugar, 2-deoxyribose in DNA and ribose in RNA.\nIn a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect and pi stacking. Specificity of which strands stay associated is determined by complementary pairing. Each base forms hydrogen bonds readily to only one other, A to T forming two hydrogen bonds and C to G forming three hydrogen bonds. The GC content and length of each DNA molcule dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association characterised by the temperate required to break the hydrogen bonding, its Tm value.\nThe cell's machinery is capable of melting or disassociating a DNA double helix, and using each DNA strand as a template for synthesizing a new strand which is nearly identical to the previous strand. Errors that occur in the synthesis are known as mutations. The process known as PCR (polymerase chain reaction) mimics this process in vitro in a nonliving system.\nBecause pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside; the two chains they form are sometimes called the "backbones" of the helix. In fact, it
625092
Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. DNA is a long polymer of nucleotides (a polynucleotide) and encodes the sequence of the amino acid residues in proteins using the genetic code, a triplet code of nucleotides.\n\nIn complex eukaryotic cells such as those from plants, animals, fungi and protists, most of the DNA is located in the cell nucleus. By contrast, in simpler cells called prokaryotes, including the eubacteria and archaea, DNA is not separated from the cytoplasm by a nuclear envelope. The cellular organelles known as chloroplasts and mitochondria also carry DNA.\n\nDNA is often referred to as the molecule of heredity as it is responsible for the genetic propagation of most inherited traits. In humans, these traits can range from hair colour to disease susceptibility. During cell division, DNA is replicated and can be transmitted to offspring during reproduction. Lineage studies can be done based on the facts that the mitochondrial DNA only comes from the mother, and the male Y chromosome only comes from the father.\n\nEvery person's DNA, their genome, is inherited from both parents. The mother's mitochondrial DNA together with twenty-three chromosomes from each parent combine to form the genome of a zygote, the fertilized egg. As a result, with certain exceptions such as red blood cells, most human cells contain 23 pairs of chromosomes, together with mitochondrial DNA inherited from the mother.
1108483
Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and many viruses. DNA is a long polymer of nucleotides (a polynucleotide) and encodes the sequence of the amino acid residues in proteins using the genetic code, a triplet code of nucleotides. DNA is thought to date back to between approximately 3.5 to 4.6 billion years ago [1].\n\nIn complex eukaryotic cells such as those from plants, animals, fungi and protists, most of the DNA is located in the cell nucleus. By contrast, in simpler cells called prokaryotes, including the eubacteria and archaea, DNA is not separated from the cytoplasm by a nuclear envelope. The cellular organelles known as chloroplasts and mitochondria also carry DNA.\n\nDNA is often referred to as the molecule of heredity as it is responsible for the genetic propagation of most inherited traits. In humans, these traits can range from hair color to disease susceptibility. During cell division, DNA is replicated and can be transmitted to offspring during reproduction. Lineage studies can be done based on the facts that the mitochondrial DNA only comes from the mother, and the male Y chromosome only comes from the father.\n\nEvery person's DNA, their genome, is inherited from both parents. The mother's mitochondrial DNA together with twenty-three chromosomes from each parent combine to form the genome of a zygote, the fertilized egg. As a result, with certain exceptions such as red blood cells, most human cells contain 23 pairs of chromosomes, together with mitochondrial DNA inherited from the mother.
276648
Prokaryotes make 38 ATP from complete oxidative breakdown of one Glucose molecule. Eukaryotes (cells with nuclei) make 36 because they hae to spend one ATP to transport both of the NADPH molecules that are created in the cytoplasm during glycolysis into the mitochondria to be used in the Electron Transport Chain.
758568
In general, organisms with less complexity, are less likely to have homeoboxes\n\nHomeoboxes seem to be reserved for higher eukaryotic cells (like human cells) that require specialized cells which will coordinate complex tasks in conjunction with other specialized cells (at least that's my simplistic viewpoint).\n\nE.coli, for example, does not contain homeoboxes because it is not dependent so much on its sister cells. \n\nI had fun thinking about the answer to your question.  Don't forget to pass on the good karma.
128363
Could be one of two things:\n\n1) a portion of the DNA is replicated so that it can be towed out of the nucleus and used to direct cellular activities.\n\n2) the entire strand of DNA is replicated at the beginning of cellular division, with one copy going to each new cell.
861120
No it doesn't. In metaphase, the chromatin (genetic material) has been duplicated (S phase of cell cycle). By the time the cell splits  and gets into the G1 phase, there is only half of the DNA there until it can get back to the S phase which is right after the G1 phase. Therefore, there should be exactly half the DNA present in the G1 phase compared to metaphase.
751672
Eukaryotic cells (typical plant and animal cells) are considered to be more advanced than prokayotic cells. Their DNA is contained within a membrane bound nucleus and they contain membrane bound organelles such as mitochondria. They also contain a cytoskeleton which is a series of tubes and microfilaments which are involved with movement within the cell.\n\nProkaryotic cells (eg. bacteria) have no membrane bound nucleus - their DNA is restricted to a region called the nuceoid which is not membrane bound. They contain no membrane bound organelles and have no cytoskeleton. They do contain non membrane bound organelles such as ribosomes ( eukaryotes also contain these)\n\nHope this is of some help.
248643
I'm not sure if you mean the "nucleus" or the "nucleolus", but either way, in cells which have a nucleus, the DNA resides here mostly because of seperation of activities in the cell - all of the enzymes used to process DNA (ie, winding and unwinding, transcription into RNA) are in the nucleus.  Other organelles in a cell, like the mitochondria or Golgi, similarly have membranes and components for specific cell activities.
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Eukaryotic cells have more membrane bound organelles, since no one wants to touch that question.
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eukaryotic, among others.
612256
Those portions of DNA are probably difficult to replicate properly (or perfectly I should say).  What's the difference between 5,000 repeats and 4,995?  Not much as far as the cell is concerned.
734251
dna is a chemical code inside every living cell that determines how the cell functions.
737692
Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the biological development of a cellular form of life or a virus. All known cellular life and some viruses have DNAs. DNA is a long polymer of nucleotides (a polynucleotide) that encodes the sequence of amino acid residues in proteins, using the genetic code.\nDNA is responsible for the genetic propagation of most inherited traits. In humans, these traits range from hair color to disease susceptibility. The genetic information encoded by an organism's DNA is called its genome. During cell division, DNA is replicated, and during reproduction is transmitted to offspring.\n\nIn eukaryotic cells, such as those of plants, animals, fungi and protists, most of the DNA is located in the cell nucleus, and each DNA molecule is usually packed into a chromosome that are passed to daughter cells during cell division. By contrast, in simpler cells called prokaryotes, including the eubacteria and archaea, DNA is found directly in the cytoplasm (not separated by a nuclear envelope) and is circular. The cellular organelles known as chloroplasts and mitochondria also carry DNA. DNA is thought to have originated approximately 3.5 to 4.6 billion years ago.[1]\n\nIn humans, the mother's mitochondrial DNA together with 23 chromosomes from each parent combine to form the genome of a zygote, the fertilized egg. As a result, with certain exceptions such as red blood cells, most human cells contain 23 pairs of chromosomes, together with mitochondrial DNA inherited from the mother. Lineage studies can be done because mitochondrial DNA only comes from the mother, and the Y chromosome only comes from the father
800985
When cells want to reproduce, they douplicate thier dna, then each identicle set of dna move to separate ends of the cell and the cell begins to pinch together in the middle to divide the cytoplasm (the stuff that fills the cells) in two, creating two identicle cells to the original cell, each with their own set of dna. This process is called mitosis.