What is a DNA

Many ask “What is a DNA?” although grammatically-speaking the question should be what is DNA?

We all know that animals give birth to the same species and this pattern is the same for almost all living creatures and plants. But why does this happen?

The answer lies in a blueprint for reproduction that every organism carries in almost every cell in its body.

This blueprint is encoded in a unique molecule called Deoxyribonucleic Acid or DNA for short.

A large number of DNA molecules are needed to carry the all the information necessary for an organism to replicate. In order to squeeze so many into each tiny cell, multiple DNA molecules are packaged up into clusters called a chromosomes.

DNA contains millions of biological instructions that determine the unique way in which every species grows and reproduces. During reproduction this genetic material, as DNA is also known, is passed from adult organisms to their offspring in the process of reproduction.

As with most other organisms, DNA is the genetic material in humans.  The DNA inside nearly every cell of a person’s body is identical. DNA is primarily found in the cell nucleus (nuclear DNA) and an organism’s complete set of nuclear DNA is referred to as its genome.

The mitochondria also carries a small amount of DNA (known as mitochondrial DNA or mtDNA).  Mitochondria are responsible for creating the energy needed by cells, and by our bodies, to function normally.

What is a DNA Sequence


What is a DNA sequenceIn order to answer the question “What is a DNA sequence?” you first need to understand how DNA molecules are constructed.

The information in DNA is stored as a code sequence comprised of four chemical molecules also known as nitrogen bases:

Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).

Human DNA contains close to 3 billion of these bases, and interestingly, more than 99 percent of those bases are identical in all human beings.

It’s the sequence in which these four bases are ordered that determines the instructions (the genetic code) for reproducing, growing and maintaining an organism.  These four bases must be present in a certain sequence in the human genome so that they “make sense,” analogous to the way in which letters of the alphabet must be present in a certain sequence so that they make sense in words and sentences.

DNA bases pair up with each other, adenine (A) pairs with thymine (T), cytosine (C) pairs with guanine (G) forming “base pairs”. The pairs are like rungs in a ladder. Each base is also attached to a sugar molecule and a phosphate molecule, and this trio is collectively called a nucleotide.  Nucleotides are chained into long spiraling strands called a double helix. The formation of the double helix resembles a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules chained to form the sides of the ladder.

Perhaps the most important aspect of DNA is that, with the help of specialized proteins and enzymes in the cell, it can replicate itself.  The two strands of DNA in the double helix serve as a master key for duplicating the entire sequence of bases in the genome, so that each new “daughter” cell receives an exact duplicate of the DNA present in the “parent” cell when one cell divides into two.


 By: Dr John Taddie