• Question: what is DNA made out of?

    Asked by yard442pup on 11 Nov 2021.
    • Photo: Frankie Macrae

      Frankie Macrae answered on 11 Nov 2021:

      There are two main components to DNA. There’s the sugar-phosphate backbone which is a very long chain made up of alternating molecules of sugar (carbon, hydrogen and oxygen) and phosphate (phosphorus and oxygen). Attached to the backbone are 4 different molecules called nitogenous bases: adenine (A), cysteine (C), guanine (G) and thymidine (T) which are made of carbon, hydrogen oxygen and nitrogen (which is why they’re called ‘nitrogenous’). The order of the As Cs Gs and Ts is the genetic sequence.
      The sugar-phosphate backbone with the attached bases is known as a DNA ‘strand’. In each DNA molecule there are two strands of DNA attached in the middle by the nitrogenous bases which looks a bit like a ladder. It’s also coiled round into a ‘double helix’ shape, a bit like a spiral staircase.

    • Photo: Becky Cohen

      Becky Cohen answered on 11 Nov 2021:

      DNA is made up of four chemical bases: Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). These bases pair up with each other, A with T and C with G, to form units called ‘base pairs’ that are held together by hydrogen bonds. Each base is also attached to a sugar molecule and a phosphate molecule – together known as a ‘nucleotide’. Nucleotides are arranged into two long strands that form a spiral known as the ‘double helix’. This structure looks a bit like a ladder – with the base pairs forming the ladder’s rungs, and the sugar-phosphate backbone forming the vertical sidepieces of the ladder.

    • Photo: Magdalena Sutcliffe

      Magdalena Sutcliffe answered on 11 Nov 2021:

      DNA is quite a complex compound. Each building block of DNA (a nucleotide) a type of sugar (deoxyribose), phosphate and an organic base. Nucleotides can bind together to form a long chain, where the sugar and phosphate form a spine and the bases stick out. Such a chain of nucleotides can then bind another chain. Then the DNA folds on itself like a twisted ladder, with the sugar and phosphate on the sides (like the rails) and the bases in the centre, like the rungs. There are 4 types of bases and they determine the message in the DNA, like letter of the alphabet or the 1 and 0 in digital codes.

    • Photo: Craig Anderson

      Craig Anderson answered on 11 Nov 2021: last edited 12 Nov 2021 2:11 pm

      There are lots of good answers here describing what DNA should be so I’ll describe what DNA sometimes is but shouldn’t be, which is relevant to my research: sometimes the nucleotides that make up a DNA molecule are damaged by chemicals or radiation and as a result interact with the rest of the DNA or proteins slightly differently. For example, cigarette smoke can cause bulky damage, incorrectly joined a.k.a. “crosslinked” DNA and even strand breaks! Fortunately we have lots of different proteins in our cells that can spot damage and do a truly amazing job of mopping up tons of damage.

      Sometimes things a bit like DNA are incorporated by mistake, for example individual ribonucleotides, or on purpose, for example short stretches of RNA which allows the cell to start copying DNA before it divides. The cell is always looking to get rid of stuff like this and lots of proteins comb through the DNA looking for mistakes to repair.

    • Photo: Frank Schubert

      Frank Schubert answered on 12 Nov 2021:

      The other answers are already very comprehensive and describe the essence of DNA as the molecule holding the genetic information.
      At a very basic level, DNA is composed of just five elements: carbon, hydrogen, oxygen, nitrogen, and phosphorous.

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