DNA is stored within the cell organelle known as the nucleus. RNA is synthesized within the nucleus using a process called transcription. During transcription, segments of DNA are used as a template to create complementary strands of RNA. The creation of RNA allows the nucleus to initiate and regulate all the activities of the cell.
What Is an Organelle?
Cells are surrounded by a membrane. Within this membrane is the cytoplasm, a jellylike fluid in which cell organelles are suspended. The term “organelle” means “little organ.” The suffix “elle” means little or small. Organelles are specialized structures that perform specific functions for the cell, in much the same manner that organs perform specific functions within the body. Some of the things organelles do include synthesizing protein, exporting cell wastes and storing energy.
There are two types of cells: prokaryotic cells (bacteria) and eukaryotic cells (multi-cellular organisms, e.g. plants and animals). Bacteria cells contain DNA (deoxyribonucleic acid), but the DNA is not organized within a particular organelle. In multi-cellular organisms, DNA is stored in the nucleus, the largest organelle within the cell. The DNA in the nucleus is responsible for the unique characteristics and activities of every eukaryotic cell.
The Structure of DNA
Nucleotides are molecules that form the basic structural unit of nucleic acids like DNA and RNA. A gene is a sequence of nucleotides arranged along a strand of DNA to form a distinct genetic code. A chain of DNA is composed of many genes with individual nucleotides. Long, spiraling strands of DNA, tightly bound together by proteins, are known as chromosomes.
The nucleolus is a spherical structure found within the nucleus of eukaryotic cells. The nucleolus is the site of ribosomal RNA synthesis. Within the nucleolus, DNA is unraveled by an enzyme known as RNA polymerase. When DNA is unraveled, RNA polymerase can access the gene sequences along the DNA strands and use them as a transcript to ultimately create protein molecules from RNA. RNA in the nucleolus is assembled into ribosomes, which are exported through nuclear pores to the cytoplasm. Ribosomes outside the cell nucleus remain free or attach to the endoplasmic reticulum.
The Purpose of RNA
RNA molecules synthesized in the nucleus perform many functions within a cell. Some RNA molecules act as catalysts in biological reactions; others control gene expression, receive and send responses to chemical signals within the cell, or activate protein synthesis outside the nucleus.