Biology

1.4 - Structure of DNA

6 min

The double helix

Nucleotides and the backboneOutside your course

Complementary base pairingOutside your course

Genes and proteins

note 1 of 1

The double helix

DNA (deoxyribonucleic acid) is the chemical that all of an organism's genetic material is made from.
It carries the coded instructions that determine an organism's inherited characteristics.
In animal and plant cells, DNA is found in the nucleus, packaged into long structures called chromosomes.

DNA is a polymer - a very large molecule built from many small repeating units joined into long chains.
These repeating units are called nucleotides.
A DNA molecule is made of two long strands.
The two strands are coiled around each other in a spiral shape called a double helix (a double-stranded spiral).
This twisted, two-stranded shape is the form DNA normally takes inside the cell.
The strands contain four different compounds called bases.
The order of the bases running down the molecule stores the coded information, so a single molecule can carry an enormous amount of instruction.

key terms

TermDefinition

DNAThe chemical that an organism's genetic material is made from. It stores the information the organism inherits.

ChromosomeA structure made of a long coiled molecule of DNA that carries many genes, found in the nucleus of plant and animal cells.

PolymerA very large molecule built from many small repeating units joined into long chains.

NucleotideThe repeating unit of DNA, made of a phosphate, a sugar, and a base.

Double helixThe twisted, two-stranded spiral shape of a DNA molecule.

end of notes

The double helix

DNA (deoxyribonucleic acid) is the chemical that all of an organism's genetic material is made from.

It carries the coded instructions that determine an organism's inherited characteristics.

In animal and plant cells, DNA is found in the nucleus, packaged into long structures called chromosomes.

DNA is a polymer with a double-helix shape

DNA is a polymer - a very large molecule built from many small repeating units joined into long chains.

These repeating units are called nucleotides.

A DNA molecule is made of two long strands.

The two strands are coiled around each other in a spiral shape called a double helix (a double-stranded spiral).

This twisted, two-stranded shape is the form DNA normally takes inside the cell.

The strands contain four different compounds called bases.

The order of the bases running down the molecule stores the coded information, so a single molecule can carry an enormous amount of instruction.