Key Points:
1. The chromosome on the left is likely to contain thousands of genes. Selecting one area of this chromosome, called the gene loci, and zooming in will show the individual strands of DNA. What you see is a double helix shape. They appear to be parallel.
2. By zooming in again, you will be able to see what's holding the two strands together. The sections on the diagram on the right are known as the sugar-phosphate backbone. In the centre there are a group of molecules called bases.
3. There are 4 different types of bases. Adenine (A), Thymine (T), Cytosine (C), Guanine (G).
4. These bases are holding together the two helix's and they're held together by A-T and G-C bonds. These are known as the base pairs. This is always found in DNA. They glue one side of the double helix to the other.
5. The order on the right side is A-C-T-G-A-A-C-C-A-G. Order of the bases. It's this order that we call the gene. The gene is inside the nucleus. Gene - Order of bases and number of bases ---> Protein in cytoplasm. And in the end this gives the characteristic. The gene is the order of the bases on one side of the double helix.