• Question: What is the main difference between chromosome, genes and DNA?

    Asked by franks23 to Gioia, Iain, Jo, Leo, Mariam on 22 Jun 2010 in Categories: .
    • Photo: Iain Moal

      Iain Moal answered on 15 Jun 2010:

      Excellent questions. DNA is a molecule which stores genetic information. Chromosomes are made up of DNA, and some parts of a chromosome are genes. Genes are made of chromosomal DNA, and they are blueprints for making different molecular machines. So, when your body needs to make a particular molecular machine, something called ‘RNA polymerase’ will go to the right part of the chromosome that has the correct gene in it, and will read the DNA, make a copy of it, send the copy to something called the ribosome, which then makes the machine.

    • Photo: Mariam Orme

      Mariam Orme answered on 20 Jun 2010:

      That’s a good question, it’s a bit confusing, isn’t it?

      DNA stands for deoxyribose nucleic acid; it’s the name of the chemical that makes up your genetic material. DNA is composed of four units that pair together, and the pairs join together in long strings. This is sometimes referred to as “the double helix”.

      If you imagine this string of DNA as thread that you might use for sewing, it’s fairly obvious that it needs to be organised in some way – we keep thread on reels, because it would just get all tangled up and be impossible to use otherwise. Similarly, each long string of DNA is wound around proteins called histones to keep it organised (though it’s a bit different from thread on a reel, because instead of the whole DNA string being wrapped round and round one histone, there are lots of histones along the length of the DNA, so it ends up looking like beads on a string. This string of DNA and histone proteins gets bundled up even further, and this is what we call a chromosome. If you want to see a drawing of what I’m trying to explain, have a look at “figure 1” on this webpage:
      http://www.nature.com/scitable/topicpage/dna-packaging-nucleosomes-and-chromatin-310
      Humans have 23 pairs of chromosomes in every cell (they’re in pairs because you get one from your mother and one from your father).

      Now, that leaves us with genes. A gene is a small section of the DNA string. If you remember, I told you that DNA is made up of four units. The order of the units is a code, containing instructions. Each stretch of DNA that we call a gene has the instructions for making a particular protein, and for determining where and when that protein will be made.

      I hope I’ve done a good enough job of explaining that, and not just made you more confused!

    • Photo: Leo Garcia

      Leo Garcia answered on 21 Jun 2010:

      A chromosome is a single piece of tightly wound DNA – and the DNA contains sequences of several genes! A human being has 23 pairs of chromosomes in the nuclei of their cells (except sperm or egg cells, which have half this number) – and around 25,000 genes (although this number is highly debated):

      http://www.ornl.gov/sci/techresources/Human_Genome/faq/genenumber.shtml

      and around 20 billion miles of DNA in all the cells (if the strands of DNA were laid end to end):

      http://www.enotes.com/science-fact-finder/biology/how-much-dna-typical-human-cell

      So, the words describe different things, but they are related.

    • Photo: Gioia Cherubini

      Gioia Cherubini answered on 21 Jun 2010:

      They are all different forms of the same thing. The DNA is the nucleic acid that contains all the instruction to produce all the proteins for the functioning of an organism. The sequence of DNA that contains the info for the expression of one protein is called gene. Within cells, the DNA is organised into structures called chromosomes

    • Photo: Joanna Watson

      Joanna Watson answered on 22 Jun 2010:

      DNA is the name for the molecule that our chromosomes are made of. A chromosome is a piece of DNA that has been coiled up in the right way to fit and work in a cell and genes are little sections on our chromosomes that give the instructions for making proteins.

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