DNA structure

• The four bases found in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).
• DNA is a double-stranded molecule that forms a helical structure.
• The sequence of nucleotides in DNA determines the genetic information carried by an organism.
• Each strand of the helix has a sugar-phosphate backbone with alternating deoxyribose sugars and phosphates, forming a "ladder" shape.
• Bases on one side of the ladder pair up with complementary bases on the other side through hydrogen bonds.
• The base pairs Adenine (A) and Thymine (T) form two hydrogen bonds between them, while Cytosine (C) and Guanine (G) form three hydrogen bonds.
• Each nucleotide has three components: a nitrogenous base (adenine, thymine, cytosine or guanine), a sugar molecule called deoxyribose, and a phosphate group.
• Each base on one strand pairs with its complementary base on the opposite strand, forming hydrogen bonds between them.
• The two strands of DNA run antiparallel to each other, meaning they have opposite orientations.
• The double helix structure allows for easy replication of DNA during cell division.
• Nitrogenous Bases are nitrogen containing molecules that act as a base, they can be either a purine or a pyrimidine
• Purines (adenine & guanine) contain two carbon and nitrogen containing rings, whereas Pyrimidines (cytosine & thymine) only contain one ring
• A purine always pairs with a pyrimidine, giving equal-sized 'rungs' on the DNA ladder
• In eukaryotic cells, most of DNA is in the nucleus. It is tightly wound around special histone proteins into chromosomes. Each chromosome is therefore one molecule of DNA.
• In prokaryotic cells DNA is in a loop and is within the cytoplasm, not enclosed in a nucleus.