However, other factors like your diet and habits also affect the risk, and we are a long way from definitively tying most diseases to precise genes, and from having tests that conclusively indicate your risk. For example, mutations in the BRCA1 and BRCA2 genes increase the risk of breast and ovarian cancer. DNA testingīecause everyone’s DNA is unique – except for identical twins – it can be used to identify people, which is why forensic scientists collect samples of blood, saliva or hair and the like at crime scenes.Īside from encoding your physical features, DNA can also reveal some of your risk for certain medical conditions. Each strand of DNA in the double helix can serve as a template for duplicating its sequence of bases, enabling new cells to be exact copies of existing ones – although mutations often occur as a result of small errors in this process. What makes DNA so amazing is that it can copy itself, which allows all known organisms to function, grow and reproduce. Mitochondrial DNA is entirely inherited from an organism’s mother. The number varies in other animals: fruit flies have only eight and the black mulberry plant has 308, for example. Humans usually have 46 of these in each cell, 23 from each parent. The coiled strands of your DNA are thus organised into chromosomes. So your three billion bases, which are more than 99 per cent the same as everyone else’s, need to be packaged up neatly. If you stretched it out, it would be almost two metres long. There is a lot of DNA packed in to every human cell. In this way, each gene tells the cell’s machinery how to make a vast array of proteins. ACT, for instance, tells cells to make an amino acid called threonine. Three bases in a row together code for a specific amino acid, the basic building blocks of proteins. The bases always pair up with the same complementary compound on the other strand of DNA: A with T, and C with G. These come in four types: adenine (A), guanine (G), cytosine (C) and thymine (T). The order of DNA’s chemical bases form the genetic code. But it was the work of many researchers throughout the decades that followed that determined what DNA codes for, how it is read, and how it is copied and passed on to new cells and future generations. It is rather like a spiral staircase or twisted ladder in which every rung is a bond between matching “bases” on its two strands. The 1953 discovery of the shape of DNA, known as a double helix, is mainly credited to Francis Crick, James Watson, Rosalind Franklin and Maurice Wilkins. We also have some DNA inside the mitochondria that power our cells, while plants have extra DNA within the chloroplasts that enable them to photosynthesise. DNA, which stands for deoxyribonucleic acid, is curled up and stored as chromosomes in the nucleus of every one of our cells. You get half of your DNA from each of your biological parents, and you will pass on a selection of half of it to any child you might conceive. DNA is the code of life, the means by which every living organism on Earth stores its genetic information.
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