DNA is sometimes called "the blueprint of life" because it contains the code, or instructions for building and organism and ensuring that organism functions correctly. Just like a builder uses a blueprint to build a house, DNA is used as the blueprint, or plans, for the entire organism.

It is the chemical component of chromosomes, which are located in the nucleus of every cell. Stretches of DNA (or stretches of chromosomes) code for genes.

Gene - a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color..etc), a gene is a stretch of DNA.

The structure of DNA was established by James Watson and Francis Crick.


The shape of the DNA molecule is a double-helix (like a twisted ladder). The sides of the ladder are composed of alternating sugars (deoxyribose) and phosphates. The rungs of the ladder are composed of nucleotides.

Nucleotides (also called Bases)

Adenine, Thymine, , Guanine, Cytosine or A, T, G, C

Nucleotides pair in a specific way - called the Base-Pair Rule

Adenine pairs to Thymine

Guanine pairs to Cytosine

Memory helper - think "A T Granite City") - which is where you live


The rungs of the ladder can occur in any order (as long as the base-pair rule is followed)

For instance, a stretch of DNA could be AATGACCAT - which would code for a different gene than a stretch that read: GGGCCATAG. All in all, there are billions of bases (nucleotides) in cells, which code for all the things an organism needs to function.


Replication is the process where DNA makes a copy of itself. Why does DNA need to copy? Simple: Cells divide for an organism to grow or reproduce, every new cell needs a copy of the DNA or instructions to know how to be a cell. DNA replicates right before a cell divides.

DNA replication is semi-conservative. That means that when it makes a copy, one half of the old strand is always kept in the new strand. This helps reduce the number of copy errors.



DNA remains in the nucleus, but in order for it to get its instructions translated into proteins, it must send its message to the ribosomes, where proteins are made. The chemical used to carry this message is Messenger RNA

RNA = ribonucleic acid.

RNA is similar to DNA except:

1. has on strand instead of two strands.
2. has uracil instead of thymine
3. has ribose instead of deoxyribose








mRNA has the job of taking the message from the DNA to the nucleus to the ribosomes.

Transcription - RNA is made from DNA

Translation - Proteins are made from the message on the RNA