• Question: How are humans made from different cells?

    Asked by anon-195785 to Judith, Gemma, Emma, Anthony on 15 Jan 2019.
    • Photo: Emma Meaburn

      Emma Meaburn answered on 15 Jan 2019:

      I’m not quite sure I fully understand your question. Are you asking how do we get different cells? (which on the face of it seems a bit unexpected, given that all cells – except from sperm and egg – contain exactly the same DNA sequence). We have ~200 different cell types, and cell type has a very specialised and specific function. Does it need to act as a barrier (skin cell) or allow signals to be passed between cells (such as neurons). Cell function is determined by how and when the information contained in the DNA sequence is accessed and used. We know this is regulated by something called ‘epigenetic’ mechanisms – a layer of chemical information that sits on top of the DNA and helps control how and when the DNA is used.

    • Photo: Anthony Redmond

      Anthony Redmond answered on 15 Jan 2019:

      We start off as a single celled zygote formed from when an egg and sperm come together. From there the genes and regulatory parts of this single cells genome control its division into two cells. These cells then are divided again, and again and so on. Very early on in this process we get stem cells are formed which can become other cell types. Other genes and as well as regulatory parts of the genomes then determine which genes get expressed and when, which determines what type of cell these stem cells will become. This is a strictly controlled process and is necessary for normal development (e.g. to make sure those legs are legs!). It happens right throughout life with many cell types, for example some immune cells change type in response to pathogens.
      We now have technology to turn our cells back into stem cells! So we could make new skin cells from liver cells for example! it’s largely down to which genes are switched on or off in a cell, which determines what proteins that cell has!

    • Photo: Judith Sleeman

      Judith Sleeman answered on 15 Jan 2019:

      We all start off as a single cell, which divides to make lots more cells. These cells start to become different types of cells by a process called differentiation. Even though all our cells have the same genes, different types of cells use different genes at different times. Some of this is decided by where the cell finds itself in an early embryo. Once a cell has been set along one pathway of differentiation, for example into skin or the brain, it usually continues down that pathway so we end up with many different cell types.

      It is possible to change this, though, in the lab and skin cells can be turned back into cells like the very early cells in the embryo and then persuaded to differentiate into different types of cell. This is really useful for studying the brain and nervous system as those are cell types that we can’t take from people.

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