DNA. Deoxyribonucleic acid A polymer Monomers are nucleotides. Nucleotides. Building blocks of DNA 4 types Each type has three parts Ring shaped sugar called deoxyribose Phosphate group Nitrogenous base Single or double ring of carbon and nitrogen atoms with functional groups.
- are larger, double ring structures called purines
This repeating pattern of sugar-phosphate-sugar-phosphate is called the “BACKBONE”
The nitrogenous bases are lined up along this backbone.
Watson and Crick model DNA this way
They created a new model in which two strands of nucleotides wound about each other.
Forming a twisting shape called the DOUBLE HELIX
Their model placed the sugar-phosphate backbones on the outside of the double helix and the nitrogenous bases on the inside.
Cytosine pairs with Guanine
While the sequence of nucleotides along the length of one of the two DNA strands can vary in a number of ways, the bases on the second strand of the double helix are determined by the sequence of the bases on the first strand.
Enzymes link the nucleotides together and form the two new DNA strands, called daughter strands.
This process of copying the DNA molecule is called
Enzymes called DNA polymerases (PAHL ih mur ayz ez) make the covalent bonds between the nucleotides of the new DNA strand.
The copying proceeds outward in both directions, creating replication "bubbles".
The parent DNA strands open up as daughter strands grow on both sides of each bubble.
DNA replication occurs before a cell divides, ensuring that the cells in a multicellular organism all carry the same genetic information.
It is also the mechanism for producing the DNA copies that offspring inherit from parents during reproduction.