There are two reasons why our DNA may change over time, although it’s important to remember that these only change the DNA in one cell, not every cell in your body will change the same way.
1) DNA is a long string of chemical letters. When cells divide to make 2 new cells, they have to make a complete copy of the DNA. This is done by copying the existing DNA ‘template’, and the copy is checked by special ‘proofreading’ machinery. However, when you are copying out 3 billion letters in every single one of about 30 trillion cells the odds are one may get missed and changed, and that’s a mutation.
2) During our lifetime, cells get damaged, most often by low levels of radiation (including UV from the sun) and by reactive forms of oxygen which are made in our cells. Occasionally in a cell one of the letters can get attacked and damaged. Each cell has special machinery to recognise this damage, and either repairs that letter, or cuts it out and replaces it with a new copy of the same letter. Sometimes though, damage is missed and when the DNA is copied the wrong letter gets put into place.
PS – Cell have another set of machinery so that if a cell gets too much damage, or can’t repair it, the cell with die so that harmful changes in the DNA are not passed on. Clever, eh?
It is. It’s how lots of cancers develop – when you get the wrong combination of mutations in the wrong cell and they escape detection, or cause some of the protective machinery to fail, you can get tumours. A lot of cancer researchers spend a lots of time looking at exactly this.
Comments
Lilyoflilyington commented on :
Thank you, this is a totally new concept for me and seems rather interesting.
Richard commented on :
It is. It’s how lots of cancers develop – when you get the wrong combination of mutations in the wrong cell and they escape detection, or cause some of the protective machinery to fail, you can get tumours. A lot of cancer researchers spend a lots of time looking at exactly this.
boppy_bat commented on :
My science teacher was doing this with us this morning!