DNA: Structure

DNA Structure and Purpose

• In simplest terms, DNA is a blueprint for life. • It is made up of genes which hold the

information for making proteins within the cell– Proteins in turn help make up everything in your

body!

• DNA is a very long polymer made up of monomers called nucleotides

• The basic 3D shape of DNA is called the double helix

• The double helix looks like a twisted ladder or zipper.

DNA’s Structure C G

A T

Sugar-phosphate backbone

Nucleotide

Hydrogen bonds

• The nitrogen bases are connected by Hydrogen bonds

• The backbone (sides) are connected by

Covalent bonds.

Covalent bonds

How is DNA held together??

1 monomer!!! Aka nucleotide

PhosphateNitrogen

baseDeoxyribose

8 monomers making a small section of DNA

• Sides of DNA are always made up of a Phosphate and 5 carbon sugar (deoxyribose).

• Middle or rungs of DNA are always made up of 4 different nitrogen base pairs.

Hydrogen bondsCovalent bonds

Nitrogenous Bases2. PURINE

– 2 rings– Adenine (A)– Guanine (G)

**Remember: “PUGA2”

1. PYRIMIDINE– 1 ring – Pyrimidines have “y”

**Remember:

*Cytosine (C)

*ThYmine (T)

Nitrogen Base pairing

• One pyrimidine and one purine will ALWAYS pair up.

• A pairs with T• G pairs with C

Location and Form of DNA• Prokaryotic DNA is located in the

cytoplasm, usually in a circular form

• Eukaryotic DNA is located inside the nucleus in the form of chromosomes

• How does all that DNA fit into the nucleus? Hopefully you remember this picture from cell division!

Review!!!• What does A pair with?

• What does C pair with?

• What makes up the sides of a the DNA strand?

• What are the base pairs held together by?

• What consists of a phosphate group, 5-carbon sugar and a nitrogen base?