What is Dna: Definition and 383 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. S

    Could human DNA be every type of plant, animal, or microbe DNA?

    I'm asking in order to understand if the only difference between the DNA of all living things is merely the arrangement or sequence of their letters. This is more of a curiosity question, not about sci-fi or current feasibility. Could the letters of a human DNA be reordered so it's identical to...
  2. G

    Calculating Shannon Entropy of DNA Sequences

    Unfortunately, I have problems with the following task For task 1, I proceeded as follows. Since the four bases have the same probability, this is ##P=\frac{1}{4}## I then simply used this probability in the formula for the Shannon entropy...
  3. G

    Micro Spring (DNA): Determine Energies, Find Expected Length

    Hi It is about a DNA strand on which there are always two segments, the segment ##A##, which is folded and has the length ##l_A## and the unfolded segment ##B##, which has ##l_B+\lambda##. Here is a section of the DNA There is now, as shown in the picture, a force ##F## pulling on the...
  4. S

    Digital logic design using DNA

  5. DaveC426913

    Valid Shapes of DNA: Is A Reasonable?

    I'm designing a ... let's call it a sculpture. It represents DNA. I just realized there are (at least) two ways helices can spiral together: A has two helices that are concentric but with different radii. They are also "in phase". B has two identical helices that are "out-of-phase" by 180...
  6. 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...
  7. nomadreid

    Confused about DNA codons

    I refer to the tables on https://en.wikipedia.org/wiki/DNA_and_RNA_codon_tables In both the DNA and the RNA codon tables, ACG codes for threonine. But the transcription of the ACG from the DNA to the mRNA ends up with UGC (which would code for Cysteine). So should I assume that when the DNA...
  8. samy4408

    A question about nucleic acids

    Hello , is minor bases and Nucleoside the same thing ?
  9. Astronuc

    Ancestry and Ancient DNA

    I recently took a DNA test in parallel with collecting family records, government records, and church records (many of which are used by local/regional governments). I knew about many ancestors, but I've confirmed many more through discovering other family lines through DNA tests. I've...
  10. moriah

    Differentiating Human DNA

    What is in our DNA that separates us from other primates?
  11. 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...
  12. I

    Biology Gel Electrophoresis of DNA fragments produced by apoptosis

    The answer is that there would only be a 250 bp fragment, and it would be brighter. I think that there would just more fragments of all sizes, as more DNA is degraded. I don't understand why there wouldn't be fragments of larger sizes. Thanks!
  13. mktsgm

    Can the AstraZeneca vaccine be called also as a DNA vaccine?

    In my understanding, in the human host, the Oxford–AstraZeneca vaccine delivers the DNA genetic code for the production of spike proteins of the SARS-CoV2 virus, inside a vector virus. DNA vaccines deliver them through plasmids. Apart from this delivery mode, is there any difference between the...
  14. Moara

    Conditional probability and criminal DNA analysis

    We know that ##P(A-) = (95\% \cdot 0.5\% + 5\% \cdot 98.5\% )## and ##P(guilty \ and \ A-) = (95\% \cdot 0.5\%)##, so letter a) is just ##P(guilty \ and \ A-)/P(A-)##. What I tried to do in letter b) was again using the conditional probability theorem. First calculating the probability that...
  15. C

    Buffer solution working with DNA -- I have to dissolve dried oligos in PBS

    This is the first time I am working with DNA and I have to dissolve the dried oligos in PBS( 10mM phosphate buffer, 100mM NaCl, ph=7.4) buffer. However I don't understand how to do that. I will really appreciate if somebody can please explain me. Thank you in advance.
  16. jedishrfu

    COVID Resistance from Neanderthal DNA

  17. H

    Biology Prokaryote DNA replication subunits

    Why (A) and (B) need to break phosphoanhydride bonds? Thanks
  18. C

    Did your DNA test results change when using a second company to do the test?

    Here's the story: I did the 23&Me and it told me that I was about 90% X but then there was among the smaller %ages a Y = French Later, about a year later, I checked it again. The French ancestry had disappeared. There was still 90% X, but now I had a Y = Scandinavia. So, I ran the test again...
  19. 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...
  20. A

    DNA sequencing and restoring malformed sequences

    I was just reading about DNA sequencing. In my view, DNA can be modeled into an ordered sequence of nucleobases, as if the two strands were joined into a single strand (just like in RNA). The first half of the sequence models the first strand. The four nucleobases are numbered from 0 to 3...
  21. J

    Does DNA get affected by the concentration of the liquids around it?

    Hi I would just like to know if DNA is affected by the concentration of liquids around it. Thanks and best regards,
  22. A

    Cumulative DNA damage in active vs. less active neurons?

    Hi all, In light of recent findings about Topoisomerase-mediated DNA double strand breaks, I have been looking for a study out there that compares cummulative DNA damage in active neurons vs. less active counterparts. So far I have not been able to find anything - this would hopefully be over a...
  23. pinball1970

    Salmon parasite has no mitochondrial DNA

    This was published in Feb https://www.pnas.org/content/117/10/5358 The genes relating to mitochondria in this parasite of Salmon are absent which is a first to see in a multi cellular animal.
  24. T

    Questions about DNA, biology, genetics and genealogy tests

    Is there any DNA, biology, genetics and genealogy tests that i can take to find out what i am supposed to do naturally OR what I am naturally made for? for example, my sexuality or being straight, bisexual, gay. If yes, what do these tests tell me about my DNA, biology and/or genes? Even if its...
  25. BillTre

    Preserved Dinosaur Cartilage: Proteins, Chromosomes and DNA Markers

    I found this article on https://www.researchgate.net/publication/339566392_Evidence_of_proteins_chromosomes_and_chemical_markers_of_DNA_in_exceptionally_preserved_dinosaur_cartilage. The reference is: Alida M. Bailleul, Wenxia Zheng, John R. Horner , Brian K. Hall, Casey M. Holliday and Mary H...
  26. A

    Fossil origin based on DNA testing

    I often read that whenever a new fossil is found (like a bone fragment or skull fragment etc) they trace it back to either some animal or human , now mostly (and before DNA testing was possible) this was done I suppose by visual inspection and "radiocarbon" dating to put the fossil in a...
  27. I

    Saving Viral DNA: B Cell Mechanisms

    Hello, I am not sure if this an odd or even an ignorant question or not, but I will give it a try. I understand that the adaptive immune system "saves viral DNA" as antibodies to potentially "use" it in the future, if the antigens ever "return". I also understand that "antigens" are "virus...
  28. Ygggdrasil

    New CRISPR-based tool for find-and-replace editing of DNA

    Over the past half decade, researchers have envisioned the https://www.physicsforums.com/insights/dont-fear-https://www.physicsforums.com/insights/dont-fear-crispr-new-gene-editing-technologies-wont-lead-designer-babies/-new-gene-editing-technologies-wont-lead-designer-babies/system as a way to...
  29. jim mcnamara

    GrimAge: methlyation DNA change, mortality

    Popular precis: https://www.aging-us.com/dna-methylation-grimage-strongly-predicts-lifespan-and-healthspan Ake Lu, Steve Horvath David Geffen School of Medicine at UCLA My take: While DNA may change anywhere due to methylation, so that cells in a given tissue may have different damage points...
  30. jedishrfu

    DNA is Held Together by a Watery Environment

  31. enorbet

    Medical DNA of Gut Bacteria Scores Hits in Autism?

    Greetings Since genome sequencing is apparently having a major impact on medical science, just to name one field, I am interested in hearing/reading more about this recent event regarding autism. It seems to me this could have far-reaching implications and possibly major impact on how we view...
  32. BillTre

    Medical "Ethics and Liabilities of Medical DNA Sequencing" -- Symposium

    As DNA sequence information from individual patients becomes more available, and the amount of information associated with particular sequence variants increases, this kind of collection and analysis of sequence data will assume great importance to medical practitioners. With medical importance...
  33. jedishrfu

    Medical The at-home DNA test craze is putting us all at risk

    Interesting video on DNA and privacy in today's world: Specifically folks in some instances can be identified from their relatives DNA. The worry of course is false positives placing you at a crime scene or of a sketchy insurance company profiling you and refusing coverage based on what...
  34. 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,"...
  35. jybe

    DNA acting like a spring

    Homework Statement A molecule of DNA (deoxyribonucleic acid) is 2.10 μm long. The ends of the molecule become singly ionized: negative on one end, positive on the other. The helical molecule acts like a spring and compresses 1.09% upon becoming charged. Determine the effective spring constant...
  36. barryj

    How is DNA arranged in a human cell?

    I have read many sources on DNA and still have a few questions. Let me start with this one, and depending on the answers I will ask more. Question 1. f I were to look into a human cell how would I see the DNA? Is there a single very long copy of the DNA string or are there two copies. Question...
  37. Genava

    Biparental Inheritance of Mitochondrial DNA in Humans

    Paternal transmission of mitochondrial DNA (mtDNA) may be possible, a new study suggests – contradicting the accepted view that it is passed on exclusively through maternal inheritance. The find, made by a team led by Taosheng Huang from Cincinnati Children’s Hospital Medical Centre, and...
  38. jedishrfu

    DNA and Big Data CAN Find You

  39. 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...
  40. Eagle9

    Eukaryotes have more freedom? (DNA)

    As we know, both strands in DNA is complementary to each other, it means that nucleotide sequence in one strand completely defines the sequence in the second strand. Bacteria has got one, circular chromosome and it contains (almost) only genes. So if there are 100 genes in one strand then...
  41. Psinter

    Are DNA and enzymes related?

    Does the human DNA contain information that could, combined with other data, tell what kinds of chemicals will their digestive system process or not? For instance, there are people that have hereditary fructose intolerance (not to be confused with fructose malabsorption). Is such a lack of an...
  42. jim mcnamara

    CRISPR and unwanted DNA alterations

    @Ygggdrasil is far more qualified to comment on this than I am, but it seems like a good idea to raise the issue. Published today July 16, 2018 Letter in Nature Biotechnology: https://www.nature.com/articles/Nbt.4192 M. Kosicki, K. Tomberg & A Bradley Abstract: In plain English this says...
  43. jim mcnamara

    DNA barcodes and genetic diversity in humans

    Very short and general precis: Analyzing the 'barcode' gene in mitochondria (big data source) has found that most current animal species have comparatively tiny genetic diversity, humans included. Based on the data, the conclusion is modern human genetic diversity is low, and modern humans as a...
  44. zexxa

    Canonical ensemble of a simplified DNA representation

    Question Form the canoncial partition using the following conditions: 2 N-particles long strands can join each other at the i-th particle to form a double helix chain. Otherwise, the i-th particle of each strand can also be left unattached, leaving the chain "open" An "open" link gives the...
  45. P

    Shiba dog's DNA found to be most similar to the Wolf but....

    https://qph.ec.quoracdn.net/main-qimg-409fb82646033d7d8ca89fc5ec6401b2-c Its behavior is not wolflike at all... How is this compatible with the DNA structure which is extremely wolf-like? Even Akita and Alaskan malamutes were less wolfy, even though they were in the top 4 - 1. Shiba 2. Chow...
  46. jerromyjon

    Do women have more DNA than men?

    I could be wrong I haven't checked, but women have 2 x's and men have an x and a y. So is an x more DNA than a y?
  47. MrGenetic

    Matching DNA subsequences

    Can be possible the transcription factor's dna binding domain's binding to two or more different DNA sequence in different(or also same) enhancers? Or there is no exception, it must be specific for dna sequence like CAATTAGTCA... for example my book says; ''MITF's binding domain can attach just...
  48. S

    Submitting your DNA to 23andMe or Ancestry.com

    Hi everyone! I have seen a number of blog entries or Youtube videos of people submitting their DNA to companies like 23andMe or Ancestry.com to find out more about their heritage. I had thought about submitting mine, and was wondering if any of you have submitted yours. If so, did you discover...
  49. G

    DNA testing, what kind of sample is the minimum?

    Is it possible to do DNA test from fallen hair, or skin cells? Or no, since the cells die and lose their core before they fall from the body? Do dead cells still have somekind of unique "fingerprint"?