DNA is short for deoxyribonucleic acid. It is a molecule found in a cells of all organisms. Most DNA molecules are found in the nucleus of each cell. They contain the genetic information that determines the structure of the cell and the way it functions. The DNA strands are bound to special proteins called histones. Each DNA is coiled around the histones. In a cell that is not dividing, the coiled DNA forms a tangled network called chromatin. When a cell divides, exact copies of each DNA molecule in the mass of chromatin must be distributed to the two daughter cells. As a cell is about to divide, the coiled chromatin becomes even more tightly coiled. These ‘super-coiled’ structures are called chromosomes. Sections of the DNA molecules make up genes. Genes contain the genetic code, which is the stored information that determines the structure of the cell.
Structure:
Each DNA molecule consists of two strands of alternating sugar and phosphates, with pairs of nitrogen bases forming cross-links between the sugar molecules. The structure is twisted into a spiral shape, called a double helix. Each phosphate group and sugar molecule with a nitrogen base attached is called a nucleotide. There are four different nitrogen bases in the DNA molecule, and they are pair only in a certain way: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). The order in which the nitrogen bases occur in the DNA molecule determines the genetic code.
Replication:
A new DNA molecule are identical to the original to ensure that inherited information is passed on unchanged when a cell is reproduced. When a cell in between cell divisions, the DNA molecules undergo replication. The linked chains of the DNA molecule separate. This can easily happen due to a weak bond. Each half then serve as a template for the nucleotides that will form the new half. The new half forms identical to the original.
Role:
The genetic code in DNA provides the instructions for protein synthesis- making proteins in the cell. The types of proteins a cell can make are determined by genes, which form parts of the DNA molecule in the nucleus. Each of the body’s cells contains identical DNA, although different genes are activated on different cells. A sequence of three bases is the code for a particular amino acid and is called a triplet. Eg. The sequence CAG (cytosine-adenine-guanine) is a DNA code for the amino acid valine.
Structure:
Each DNA molecule consists of two strands of alternating sugar and phosphates, with pairs of nitrogen bases forming cross-links between the sugar molecules. The structure is twisted into a spiral shape, called a double helix. Each phosphate group and sugar molecule with a nitrogen base attached is called a nucleotide. There are four different nitrogen bases in the DNA molecule, and they are pair only in a certain way: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). The order in which the nitrogen bases occur in the DNA molecule determines the genetic code.
Replication:
A new DNA molecule are identical to the original to ensure that inherited information is passed on unchanged when a cell is reproduced. When a cell in between cell divisions, the DNA molecules undergo replication. The linked chains of the DNA molecule separate. This can easily happen due to a weak bond. Each half then serve as a template for the nucleotides that will form the new half. The new half forms identical to the original.
Role:
The genetic code in DNA provides the instructions for protein synthesis- making proteins in the cell. The types of proteins a cell can make are determined by genes, which form parts of the DNA molecule in the nucleus. Each of the body’s cells contains identical DNA, although different genes are activated on different cells. A sequence of three bases is the code for a particular amino acid and is called a triplet. Eg. The sequence CAG (cytosine-adenine-guanine) is a DNA code for the amino acid valine.
Build your own DNA molecule:
http://learn.genetics.utah.edu/content/molecules/builddna/
http://learn.genetics.utah.edu/content/molecules/builddna/