DNA DNA NotesNotes

History of DNA

• James Watson and Francis Crick are given most of the credit for discovering the structure of DNA

• They used x-rays from Rosalind Franklin

determine the spiral shape

The Evidence and Models

• Rosalind Franklin’s Watson and Crick’s

X-ray of DNA original model

What is DNA Made Of?

• The backbone of DNA is made of:– Phosphate – Deoxyribose (sugar)

** These molecules alternate all the way down the side of the molecule

What’s in the middle?

• There are four base molecules– Adenine (A)– Thymine (T)– Cytosine (C)– Guanine (G)

• The bases form specific pairs– Adenine pairs with thymine (A-T) or (T-A)– Cytosine pairs with guanine (C-G) or (G-C)

Here is the full picture!

Nucleotides

• Nucleotides are the pieces that make up a strand of DNA

• Each nucleotide is made of:– A sugar (deoxyribose)– A phosphate– A base

Replication

• DNA replication occurs when a copy of the DNA is made

• Replication occurs during mitosis and meiosis

• If all goes well, the copy is identical to the original strand of DNA

Mutations

• A mutation is a mistake in the DNA that usually occurs during replication

• Not all mutations are harmful

• Types of mutations:– Insertion– Deletion– substitution

Insertion

• Extra bases are added to the strand

Deletion

• Bases are left out of the strand of DNA

Deletion

• Entire sections of chromosomes can be deleted

Substitution

• Bases are replaced with

different bases

Ex: sickle cell anemia

Substitution, con’t