Facts About DNA

Facts About DNA

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DNA stands for the chemical deoxyribonucleic acid.

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DNA is the chemical which stores genetic information
in all living cells.
DNA from all organisms is made up of the same chemical and physical components.

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Double helix structure: 
DNA can be pictured as an extremely long ladder that has been twisted into the double helix shape or spiral staircase.

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The sides of the ladder or double helix are a linked chain of alternating sugar and phosphate molecules. 

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The rungs
of the ladder are made of a pair of molecules
 called bases that are weakly attracted to each other. 

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There are 4
different bases- adenine, thymine,
cytosine, and guanine (A,C,T, G for short). 

·       
The 4 DNA bases
can pair with each other, but only in
certain combinations.  A pairs with T.  C pairs with G. 

·       
A:T and C:G are
said to be complementary base pairs

·       
The 2 DNA
strands in a helix are complementary strands

·       
The sequence of
the bases determines the genetic information. The
DNA
sequence is
the particular side-by-side arrangement of bases along the DNA strand (e.g.,
ATTCCGGA). This order spells out the exact instructions required to create a
particular organism with its own unique traits.

·       
DNA in the
human genome is arranged into 23 pairs of

chromosomes--physically
separate molecules that range in length from about 50 million to 250 million
base pairs. 

·       

Genes
are the basic physical and functional units of heredity. A gene is a specific
sequence of bases that encode instructions on how to make a protein. The human
genome is estimated to contain 20,000-25,000 genes.

·       
Proteins
are the workhorses in a cell.
Proteins
perform most life functions and make up the majority of cellular structures.
Proteins are large, complex molecules made up of smaller subunits called amino
acids. There are 20 different amino acids, each with unique
chemical properties.  Just as the sequence of DNA bases in a gene determines the
gene’s function, the sequence of amino acids in a protein determines its
chemical properties.  Linear protein chains fold up into specific
three-dimensional structures that define their particular functions in the cell.

·       
The
genome
is an organism’s complete set of DNA. Genomes vary widely in size. The smallest
known genome for a free-living organism (a bacterium) contains about 600,000 DNA
base pairs, while human and mouse genomes have some 3 billion.

·       
Cells
are the fundamental working units of every living system. All the instructions
needed to direct a cell’s activities are contained within the chemical DNA
(deoxyribonucleic acid).

·       
There are 3
billion bases (A,C,T,G) in the DNA code of a human.

·       
A person has
about 9 million kilometers of DNA in her body.