DNA structure and making proteins
The structure of DNA
James Watson and Francis Crick worked out the structure of Deoxyribonucleic acid. The material inside the nucleus of cells, carrying the genetic information of a living being. in 1953. By using data from other scientists (Rosalind Franklin and Maurice Wilkins) they were able to build a model of DNA. The X-ray crystallography data they used showed that DNA consists of two strands coiled into a The shape of the DNA molecule, with two strands twisted together in a spiral..
Image caption, The famous X-ray diffraction photograph of DNA taken by Rosalind Franklin, known as photograph 51
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DNA is a polymer made from four different The units or molecules of which DNA or RNA is composed. These are arranged in a repeating fashion. Each nucleotide consists of alternating sugar and phosphate sections with one of the four different bases attached to the sugar.
Base pairs
Each strand of Deoxyribonucleic acid. The material inside the nucleus of cells, carrying the genetic information of a living being. is made of chemicals called bases. Note that these are different to bases in relation to acids and alkalis in chemistry. There are four different bases in DNA:
- thymine, T
- adenine, A
- guanine, G
- cytosine, C
There are chemical bonds between the two strands in DNA, formed by pairs of bases. They always pair up in a particular way, called complementary base pairing:
- thymine pairs with adenine (T鈥揂)
- guanine pairs with cytosine (G鈥揅).
The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production. are sections of the DNA. Each gene has the code for creating a specific Organic compound made up of amino acid molecules. One of the three main food groups, proteins are needed by the body for cell growth and repair.. The sequence of bases in the gene controls which The building blocks that make up a protein molecule. are joined in order to make a specific new protein (or enzyme) molecule. The proteins are then folded into their correct shape to make them functional.
Making proteins from amino acids
Each gene acts as a A rule for converting one type of information into another, usually simpler or more complicated. , or set of instructions, for making a particular protein. Some of these proteins control the cell's internal chemistry. They tell the cell what to do, give the organism its characteristics, and determine the way its body works.
To enable genes to code for proteins, the bases A, T, G and C get together - not in pairs - but in triplets. This is how it works:
- Each triplet of bases codes for one particular amino acid.
- Amino acids are made in the number and order dictated by the number and order of base triplets.
- The amino acid molecules join together in a long chain to make a protein molecule. The number and sequence of amino acids determines which protein is produced.
Each protein is made up of large numbers of amino acid molecules. Since many of the proteins made are enzymes, genes control the cell's internal chemistry.