• Question: What is the cell cycle?

    Asked by Elisabethcabanas to Tom, Paul, Ester, Eoin on 6 Nov 2017.
    • Photo: Paul McKeegan

      Paul McKeegan answered on 6 Nov 2017:

      It’s a routine that most cells in the body go through as part of their normal function and as part of producing more cells to grow as a whole organism. There are three main parts: Interphase – where the cell grows and replicates its DNA, Mitosis – when the cell arranges its DNA in the form of chromosomes ready to separate, and cytokinesis – when the cell splits into 2 daughter cells, each with the right DNA and an even share of the organelles, like mitochondria and ribosomes. There are ‘checkpoints’ at different stages of this, which help prevent things going wrong. When the cell cycle loses this control, it can lead to cancer. I bet the others can add to this!

      In egg and sperm cells, the cell cycle is a bit different. Instead of creating 2 daughter cells with a complete set of paired chromosomes (DNA), a cell called a progenitor cell divides to give us an egg or a sperm with an unpaired set of chromosomes, or half the regular amount. The egg sits like this (we call it meiotic arrest) in the ovary for many years, from before birth until it is eventually ovulated and fertilised to make a zygote, or fertilised egg, with a complete set of chromosomes. Eggs are really precious! Its a bit different in the male as sperm are constantly produced and destroyed.

    • Photo: Ester Gil Vazquez

      Ester Gil Vazquez answered on 6 Nov 2017:

      I don’t think I can add much to what Paul said regardless the cell cycle itself (good job). The cell cycle is the mechanism by which cells grow and divide to generate copies of themselves. In order to do this, cells need to duplicate their DNA so that each of the daughter cells can get a copy. Sometimes, we make mistakes while copying the DNA and change the code (these changes are called mutations). Although our cells are really good at correcting these mistakes, they fail sometimes. When this happens, the two daughter cells are not completely identical, but still quite similar (most of the times it doesn’t have any effect in the function of the cell)
      Cells need to divide a lot while we are young since our body is growing. When we get to the adult stage, many cells stop dividing and only small pools keep doing it to maintain the body in a good shape. As Paul said, the cell cycle is very well regulated and if it gets out of control this can lead to excessive division of cells. Sometimes, the body is able to detect and eliminate the mass of cells, but others it continues growing, dividing and accumulating mutations until it becomes a cancer.

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