Dna Definition and 126 Discussions

Deoxyribonucleic acid ( (listen); DNA) is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses. DNA and ribonucleic acid (RNA) are nucleic acids. Alongside proteins, lipids and complex carbohydrates (polysaccharides), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life.
The two DNA strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides. Each nucleotide is composed of one of four nitrogen-containing nucleobases (cytosine [C], guanine [G], adenine [A] or thymine [T]), a sugar called deoxyribose, and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds (known as the phospho-diester linkage) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups, pyrimidines and purines. In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine.
Both strands of double-stranded DNA store the same biological information. This information is replicated as and when the two strands separate. A large part of DNA (more than 98% for humans) is non-coding, meaning that these sections do not serve as patterns for protein sequences. The two strands of DNA run in opposite directions to each other and are thus antiparallel. Attached to each sugar is one of four types of nucleobases (or bases). It is the sequence of these four nucleobases along the backbone that encodes genetic information. RNA strands are created using DNA strands as a template in a process called transcription, where DNA bases are exchanged for their corresponding bases except in the case of thymine (T), for which RNA substitutes uracil (U). Under the genetic code, these RNA strands specify the sequence of amino acids within proteins in a process called translation.
Within eukaryotic cells, DNA is organized into long structures called chromosomes. Before typical cell division, these chromosomes are duplicated in the process of DNA replication, providing a complete set of chromosomes for each daughter cell. Eukaryotic organisms (animals, plants, fungi and protists) store most of their DNA inside the cell nucleus as nuclear DNA, and some in the mitochondria as mitochondrial DNA or in chloroplasts as chloroplast DNA. In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm, in circular chromosomes. Within eukaryotic chromosomes, chromatin proteins, such as histones, compact and organize DNA. These compacting structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.

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  1. K

    Genetic code other than DNA (moved)

    Summary: Curious to find out genetic code other than DNA <mentor> Moved to Discussion, hypothetical discussion Dear PF Forum, It's been a long time since I log into PF. And I hope everybody is in a good health. Recently I had a discussion debate with my friend about other life in this...
  2. samy4408

    A question about nucleic acids

    Hello , is minor bases and Nucleoside the same thing ?
  3. mktsgm

    Medical What determines the long-term effectiveness of a viral vaccine?

    It is well known that RNA viruses mutate very quickly. Hence, it is said that it is very hard to develop an effective vaccine against it. With HIV and influenza RNA viruses the scientific world is still facing difficulty in developing effective long-term vaccines against them. Most influenza...
  4. entropy1

    Recombining DNA in reproduction

    I understand that DNA strands have two sides with amino acids, and that the amino acids connect to each other by being the opposite of each other (A-T, C-G). I also understand that the reproductory DNA of the organisms reproducing each consist of one side of each of the DNA strands, that...
  5. Ygggdrasil

    Researchers double the size of the DNA alphabet

    Published this week in the journal Science, researchers report that they have devised a eight letter alphabet for DNA and RNA: The work builds off of previous work, which had expanded the genetic alphabet to six letters. The researchers call their eight-lettered nucleic acids "hachimoji,"...
  6. Navin

    What makes the DNA Double Helix Possible

    Homework Statement The Reason for the Double helical Structure of DNA is the operation of - A) Van Der Waals Forces B)Dipole Dipole Interactions C)Hydrogen Bonding D)Electrostatic Attraction 2. Background of question This question ,is part into the home work asignment my chem tracher...
  7. Ygggdrasil

    Semi-synthetic organism with an expanded genetic code

    All life on Earth stores its genetic information in DNA using just four nucleotide letters: A, T, C, and G. Research published this week in the journal Nature describes how scientists engineered a bacterium to incorporate two new letters into their DNA (which they call X and Y, pictured below)...
  8. klotza

    Insights New Research on Untying Knots in Polymers - Comments

    Greg Bernhardt submitted a new PF Insights post New Research on Untying Knots in Polymers Continue reading the Original PF Insights Post.
  9. klotza

    Insights Using the Spaghetti-Twist to Align DNA - Comments

    Greg Bernhardt submitted a new PF Insights post Using the Spaghetti-Twist to Align DNA Continue reading the Original PF Insights Post.
  10. T

    What is the length of Chromatosomal DNA?

    I see various sources: 1. Karp- Cell biology 2. some papers 3. Michael M. Cox -...
  11. I

    Why proteins and DNA aren't organelles?

    Hi, when I look up organelles listed, DNA and proteins are not in that list. How come? Aren't they "specialized subunit within a cell that have specific functions" too? Then I see ribosome made it to the list. Why is that protein more special than others? Why not put RNA Polymerase in there...
  12. I

    Proteins that duplicate the DNA in interphase

    For some reason, I can't seem to be able to find this answer easily on the internet. Or it is there and I somehow I can't see the wood for the trees. I know that in transcription (when DNA is read for protein production), "RNA polymerase" is the protein that creates the mRNA by creating the new...
  13. C

    How intimately can we observe DNA replication?

    I found this interesting computer animation representing DNA functions in cells. My questions: 1) How precisely can we actually magnify cell functions, and what is preventing us from peering in as closely as depicted in the video (keeping in mind that I know it's probably technologically...
  14. klotza

    Insights Polymer Physics and Genetic Sequencing - Comments

    klotza submitted a new PF Insights post Polymer Physics and Genetic Sequencing Continue reading the Original PF Insights Post.
  15. B

    DNA Topology

    Homework Statement Suppose that a turn of B-DNA in a circular DNA molecule with L = 100 and W = -4 becomes a turn of Z-DNA . a) What are the L, T, and W following the transition? Homework Equations L=T+W L=#bp/#bp/turn B-dna= 10.4bp/turn Z-dna=12bp/turn The Attempt at a Solution...
  16. I

    Can DNA from an animal ever end up in bacteria or viruses?

    I was wondering if it is possible for a bacteria to enter a body and somehow get some amount of that animal's DNA in itself if and when it leaves the body? Or if it just continues to live in the body. Basically does DNA ever linger around? I heard about "DNA dropping" in organisms, if that's the...
  17. Stephanus

    B Extra Terrestial Life Form

    Dear PF Forum, I would like to know if LIFE in exoplanet is possible. And if it is, how? When I drove my Pastor to my mother funeral, he asked me out of the blue while I was driving my car. "Do you believe there is another earth?" My immediate response would be, in parallel universe where there...
  18. I

    Can gene structure determine its "strength"?

    Are certain DNA (genetic) strands structurally better build for survival than others? If yes, is there a term for this? For example, is there a specific order of nucleotides that is harder to destroy than another? Or if there is a specific order/combination of nucleotides that would have...
  19. B

    Eye heredity

    Hello, In the picture above a couple are shown with their children. Or are they actually their children? Is it possible for them, having green (?) and hazel (?) eyes, to get 1 child with blue eyes and 3 children with brown eyes?
  20. I

    What gives DNA replicating ability?

    I am wondering about the actual preconditions that give rise to DNA replication. Basically, what are the actual environmental conditions/factors that created the process of replication in the first place. I gather before replication, there was random atom and molecule sorting, and at some...
  21. I

    DNA in inanimate objects?

    I couldn't find much on this topic online. Besides their basic chemical structure, can inanimate objects be said to contain DNA molecules? They don't have to genetically replicate (or at least not quickly). Thanks for any thoughts! :)
  22. F

    DNA modification

    This is pretty cool. Imagine people being able to alter DNA at will. http://www.nature.com/news/chinese-scientists-genetically-modify-human-embryos-1.17378
  23. F

    Immortality: Stop DNA Aging or Swapping Consciousness?

    I know there are similar threads regarding the topics above, but which method do you think is more achievable within the next decade? With the current ways of supercomputer and computing in decoding DNA as well as brain mapping, it might be a possible reality in the future.
  24. V

    Foreign cells can they survive and divide using its own dna

    If a foreign human cell is introduced into one's body by way of blood transfusion or through some other method could these foreign cells survive and take up host in their new environment ? So if a foreign nerve cell is introduced could this nerve cell take up host as a native cell where it can...
  25. Anand Wilson

    Can we break the hydrogen bonds in DNA with Phonon?

    Double stranded DNA are bind with hydrogen bonds in between the nitrogenous bases, Usually we use high temperature for denature,so can we break the hydrogen bonds with phonon because shorter wavelength give rise to heat, weather it is possible to denature the DNA?
  26. I

    Neurons, DNA, Memory and Learning

    Hello I am not an expert in this field but I am really hoping to understand as much as I can about the concepts described in my questions below. I might be using some improper jargon and expressions, so I apologize if some things are incorrect or confusing. #1 Do all the neurons have the same...
  27. V

    Genetic Code Question

    Homework Statement Val-tRNA val is the tRNA that carries valine to the ribosome during translation. Which of the following sequences gives an appropriate anticodon for this tRNA? A. CAU B. AUC C. UAC D. GUG Homework Equations There are four different codons for Valine: GUU, GUC, GUA, and...
  28. S

    New DNA Sequencing Technology

    New DNA sequencing technology allows the human genome to be sequenced in a matter of days: http://www.stltoday.com/lifestyles/health-med-fit/medical/new-technology-at-wash-u-maps-human-genome-in-days/article_9ed22975-a385-5b53-897a-ff88cba2442b.html Maybe the Twenty-First Century is starting...
  29. Ygggdrasil

    Making a Voltron out of DNA

    A figure in a recent paper from Science made me smile, so I thought I'd share it with you guys. The paper describes a new way of joining nanoscale building blocks together using DNA origami. It's based on the principle that if you have two DNA double helices with a gap in between (see the blue...
  30. T

    Can information be added to DNA?

    Hi I'm debating a creationist and he makes the claim that no DNA can be added to a genome. Says there are no experiments. Can someone help me with concepts or sources to experiments? Thanks
  31. V

    History of NIH DNA Policies

    I have one question about the history of the policies regarding DNA privacy the NIH has instituted. Simply, was there a particular study or research breakthrough that was the tipping point for instituting privacy measures? I just read an ethics paper called "Privacy and the Human Genome...
  32. S

    Hydrogen bonding force problem

    Homework Statement In a DNA molecule, the base pair adenine and thymine is held together by two hydrogen bonds (see figure below). Let's model one of these hydrogen bonds as four point charges arranged along a straight line. Using the information in the figure below, calculate the...
  33. s@Ed-biophysics

    DNA nano wire

    Hi there Is there anyone to help me about a definition of "DNA nano wire"?!
  34. J

    Can you replace a cell's dna?

    In cloning, they replace the cells nucleus, but what if you only have pure dna, could you somehow, switch it for the cells own dna?
  35. P

    DNA in Cut Hair ?

    Is it true that hair that is cut from your head (not pulled), does not contain any nuclear dna ? My understanding of hair structure is that it is a matrix with at least some dead cells present in various layers. Eg the outside cuticle is made of flattened cells . Feughelman, Max Mechanical...
  36. M

    Biocomputers: DNA as memory

    Is there any research being done on using DNA or big long protein macromolecules as machinery for memory in computing? The ability to pack in so much information in a long string of protein because of how proteins can fold is vast. Has anyone proposed making DNA that into a binary entity, like...
  37. M

    Chemistry Determining the Length of DNA Molecules Biology Lab Question

    Homework Statement The length of DNA helix occupied by one nucleotide pair is 3.4 A (angstrom). A human has 10^14 cells and each human cell has about 6.4 x 10^9 nucleotide pairs of DNA. What is the length of double helix that could be formed from this amount of DNA in a human individual...
  38. A

    Placement of chromosomes from each parent on dna

    is dna in a sexually reproducing organism one single chain with dna from one parent coming first,with the other parent's dna joining it as it ends.or do the two strands lie side by side,without joining.Or do they lie side by side and join at some point? the purpose of asking the question is...
  39. J

    Possible Uses of Bacterial DNA Replication

    Homework Statement Not exactly homework... "What are the uses of bacterial DNA replication in molecular biology?" The Attempt at a Solution Am I correct to say that 'the bacterial DNA replication process can be used to artificially create DNA that we desire and then use it for some...
  40. L

    When you insert DNA into a bacteria, why does it make your protein?

    So we are learning about vectors and how you can insert vectors into a plasmid and then that plasmid in a bacteria will make lots of copies of the protein that your sequence codes for. I don't understand how inserting the DNA that codes for a protein into a bacteria gives you just the protein...
  41. Biosyn

    How is a specific gene removed from DNA

    I was reading an article on Pseudomonas syringae and how removing a gene called inaZ from it's DNA will allow it to be sprayed on crops to prevent the crops from freezing during the winter. How is the inaZ gene removed from the DNA? I'm thinking that they use restriction enzymes that cut out...
  42. Greg Bernhardt

    Home DNA test kits

    Has anyone used a home DNA testing service? I was looking at 23andme service. The reviews are pretty good and it's only $100. Could be interesting. What do you experts think? Worthwhile?
  43. Z

    How to design DNA chip?

    May I know how to design the DNA chip? What are the basic parameter I have to consider? The DNA chip will be used in microfluidic chamber for cells analysis. Thanks zmp
  44. Ahmed Abdullah

    Can you explain how vigorous vortex-ing can damage DNA?

    I want to know what is happening at micro-level, how macroscopic tumbling of the solution can actually break a chemical bond?
  45. S

    Which was the origin, DNA, RNA or Protein?

    Hello! I'm looking for information, articles and theories about which could have been the original molecule of life: DNA, RNA or protein. Most of what I've found is based on the RNA world theory (which I think is pretty well explained and sounds plausible), but I haven't found out any...
  46. A

    Recombinant dna technology-[how are specific genes chosen]?

    Recombinant dna technology-[how are specific genes chosen]?? IN recombinant dna technology,certain segments of dna are removed from one organism and put in another.How are are specific portions of DNA removed from certain animals and fused into others?? More importantly,how do scientists know...
  47. W

    DNA mismatch repair

    i understand that methylation helps to differentiate between parental strand and daughter strand with mismatch nucleotides. (newly synthesised DNA is hemimethylated) then GATC endonuclease and GATC exonuclease will nick the mismatch nucleotide sequences. however, i don't understand how the...
  48. C

    DNA Fingerprinting: Genome variability

    How much variability exists between the genomes of separate individuals? What is an SNP?
  49. D

    Scientists Examining DNA of Centenarians

    http://news.yahoo.com/longevitys-secrets-sought-dna-100-olds-203909753.html Apparently, there's something good in their genes! "By the time you reach, say, 105, "it's very hard to get there without some genetic advantages," says Dr. Thomas Perls, a geriatrics expert at Boston University."...
  50. D

    Compare the structure of RNA and DNA with respect to the following characteristics.

    Homework Statement 3) Compare the structure of RNA and DNA with respect to the following characteristics. Length Function Molecular components Homework Equations The Attempt at a Solution I know nothing about the length, Function: RNA reads the info in DNA and transports...