Tin is a malleable silvery-white metal which takes a high polish. It possesses a highly crystalline structure and is moderately ductile. When a bar of tin is bent, the crystals break, producing a characteristic 'tin cry'. Two or three allotropic forms of tin exist. Gray or a tin has a cubic structure. Upon warming, at 13.2Â°C gray tin changes to white or b tin, which has a tetragonal structure. This transition from the a to the b form is termed the tin pest. A g form may exist between 161Â°C and the melting point.
The particular order of the bases arranged along the sugar-phosphate backbone is called the DNA sequence; the sequence specifies the exact genetic instructions required to create a particular organism with its own unique traits. Each strand of the DNA molecule is held together at its base by a weak bond.
It makes it easier to load the samples and visually track the migration of DNA through the gel. 4. Explain why DNA has an overall negative charge. Phosphate groups in the DNA backbone carry negatively-charged oxygen molecules giving the. phosphate-sugar backbone of DNA an overall negative charge. 5.