DNA STRUCTURE:
The structure of DNA is a double helix model. It consists of two strands, which are winded around each other, resembling a twisted ladder. These strands consist of alternating sugar (deoxyribose) and phosphate groups. Attached to the sugar and phosphate molecule is a nitrogenous base. There are four nitrogenous bases:
- Adenine (A)
- Cytosine (C)
- Guanine (G)
- Thymine (T)
These bases pair up with each other and are held together by hydrogen bonds. However, there are strict rules for their pairing. Adenine (A) will only pair up with Thymine (T), and Cytosine (C) will only pair up with Guanine (G).
Together, the deoxyribose, phosphate and nitrogenous base are referred to as nucleotides. Many of these units join together to create the DNA molecule, and two nucleotides joined together are referred to as a base pair. They derive their names from the nitrogenous bases that they contain, however, most of their structure and bonding capabilities derive from their deoxyribose molecule. This molecule contains five carbon atoms and one oxygen atom. These are arranged in the shape of a pentagon, resulting in one of the carbon atoms jutting out from the structure. The phosphate group attaches to this carbon atom, and the nitrogenous base attaches to one of the carbon atoms.
- Adenine (A)
- Cytosine (C)
- Guanine (G)
- Thymine (T)
These bases pair up with each other and are held together by hydrogen bonds. However, there are strict rules for their pairing. Adenine (A) will only pair up with Thymine (T), and Cytosine (C) will only pair up with Guanine (G).
Together, the deoxyribose, phosphate and nitrogenous base are referred to as nucleotides. Many of these units join together to create the DNA molecule, and two nucleotides joined together are referred to as a base pair. They derive their names from the nitrogenous bases that they contain, however, most of their structure and bonding capabilities derive from their deoxyribose molecule. This molecule contains five carbon atoms and one oxygen atom. These are arranged in the shape of a pentagon, resulting in one of the carbon atoms jutting out from the structure. The phosphate group attaches to this carbon atom, and the nitrogenous base attaches to one of the carbon atoms.
DNA Replication:
Due to the unique structure of DNA, it is able to make copies of itself during cell division. When a cell prepares to divide, the hydrogen bonds holding the base pairs together are broken apart by a special enzyme known as helicase. This causes the helix model to split down the middle, creating two single strands. Each separated section contains half the amount of original information and acts as a "template" for the production of the opposite strand. Thus, a C base is added wherever a G base exists, and an A base is added wherever a T base exists. This creates two new single strands, which are capable of joining up and creating a new DNA molecule.