I have a very basic question, but it seems the hardest to me. So we have 46 chromosomes (23, 2 copies of each). Do all chromosomes have the same DNA? If so, does it mean that in different cells with different functions some genes are expressed and some aren't? Also, if each chromosome has different lets say "fragment" of the genome, how is the genome interconnected?

  • Welcome to SE Biology. Please take the time to read the tour and, especially how to ask questions here. One key point is that you are expected to research questions before asking. What texts have you consulted. Have you looked at pictures of human chromosomes and observed whether they are of similar size, for example? Try searching NCBI bookshelf, e.g. Molecular Biology of the Cell – David Jul 14 at 3:43

Do all chromosomes have the same DNA?

No. Not any more than each chapter of a book has the same words in the same order.

If so, does it mean that in different cells with different functions some genes are expressed and some aren't?

Yes. In general, all cells in your body have all the same DNA; what makes your retina cells function differently from your pancreatic beta cells is which genes they express. Like if every chef in a restaurant had the same recipe book which had every recipe the restaurant can make, but the pastry chef only makes pastries.

Also, if each chromosome has different lets say "fragment" of the genome, how is the genome interconnected?

The genome is not physically connected except for all the genes on a chromosome being physically connected. But a gene product from one chromosome might control expression of another gene by physically binding to the DNA close to it, which can affect its expression. But most gene-gene interactions are really protein-protein interactions. (Or in some cases, RNA interacting with RNA)

  • Well used analogies and nice short answers to simple, broad intro questions! +1 – Remi.b Jul 13 at 23:12

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