What Are the Three Bases Along the DNA Strand a Sequence For?

DNA Structure

• DNA represents the entire genetic code needed for producing everything within the human body, including each person's unique characteristics. A single strand of DNA is built from alternating deoxyribose sugars and phosphates, creating a backbone. However, each sugar also bonds to one of four different bases: adenine, guanine, cytosine or thymine. A group of one sugar, phosphate and base is called a nucleotide. Two strands of DNA are then joined together at the bases to form the iconic double-helix shape, with the bases representing the rungs on the DNA ladder. There are millions or billions of individual bases in each stand of DNA.

DNA Bases

• DNA bases, also known as nucleotide bases, only cross-link with each other in a very specific order. Adenine only bonds to thymine, and cytosine only bonds to guanine. This enables DNA to replicate by splitting while still maintaining the exact sequence on each strand. The bases represent the alphabet of life. Their sequence provides the instructions for building the more than 100,000 proteins the human body needs in order to function.

Base Triplets

• Bases are organized into groups of three, called triplets or codons. This creates 64 possible combinations. Each triplet represents an acid or a control code used in the protein synthesis process. While each triplet represents a unique amino acid, each of the 20 amino acids may have up to six corresponding triplets, providing redundancy in the genetic code. When used as control codes, they signal when to start or stop constructing a protein. This typically occurs at the beginning or end of a gene. A gene is a small segment of DNA that contains the triplet code for a given protein. The base triplet code is universal, meaning it is the same in almost all organisms.

Protein Synthesis

• Proteins are constructed from the sequence of bases in two stages. Transcription is the first stage and involves the duplication of a DNA gene code, creating a stand of messenger RNA. Multiple copies can be produced, depending on the amount of protein needed. The messenger RNA leaves the cell nucleus, where it links up with ribosome RNA. The messenger RNA serves as the protein blueprint while the ribosome RNA functions as the protein factory. Transfer RNA reads each base triplet and delivers the corresponding amino acid to the factory, where the ribosome RNA bonds them together to form the required protein.