What is this DNA you speak of?What is this DNA you speak of?

DNA stands for deoxyribonucleic acidDNA stands for deoxyribonucleic acid- Found in nucleus of eukaryotic cells- Found in nucleus of eukaryotic cells

- Found in cytoplasm of protists- Found in cytoplasm of protists

Why should I care about DNA?Why should I care about DNA?

Two main functionsTwo main functions

1.) Stores the genetic information of an 1.) Stores the genetic information of an organism.organism.

Why should I care about DNA?Why should I care about DNA?

Two main functionsTwo main functions

2.) Contains instructions for how to construct 2.) Contains instructions for how to construct important biological molecules.important biological molecules.

Example: Building new cellsExample: Building new cells

What is the structure of DNA?What is the structure of DNA?

Twisted ladder-like shape called a Twisted ladder-like shape called a double helixdouble helix

Three main componentsThree main components

1.) Phosphate group1.) Phosphate group

2.) 5 carbon sugar2.) 5 carbon sugar

3.) Nitrogenous base3.) Nitrogenous base

What is the structure of DNA?What is the structure of DNA?

Three main componentsThree main components

1.) Phosphate group1.) Phosphate group

2.) Five carbon sugar2.) Five carbon sugar

3.) Nitrogenous base – Four types3.) Nitrogenous base – Four types

- Adenine- Adenine

- Guanine- Guanine

- Cytosine- Cytosine

- Thymine- Thymine

DNA ‘backbone’

“Purines”

“Pyrimidines”

Nitrogenous BasesNitrogenous Bases1.) Purines1.) Purines

- Adenine- Adenine - Guanine- Guanine

2.) Pyrimidines2.) Pyrimidines- Cytosine- Cytosine - Thymine- Thymine

The sequence of the nitrogenous basesThe sequence of the nitrogenous basesin DNA determines the genetic code!in DNA determines the genetic code!

Nitrogenous BasesNitrogenous Bases Base PairingBase Pairing

- Purines - Purines ALWAYSALWAYS bond with bond with

pyrimidines!pyrimidines!

Chargaff’s Rules:Chargaff’s Rules:- Adenine ALWAYS bonds with thymine- Adenine ALWAYS bonds with thymine

A---TA---T

- Cytosine ALWAYS bonds with guanine- Cytosine ALWAYS bonds with guanine

C---GC---G

The amount of A = amount of TThe amount of A = amount of T

The amount of C = amount of GThe amount of C = amount of G

What is the structure of DNA?What is the structure of DNA?

What is the structure of DNA?What is the structure of DNA? A single strand of DNA has a 5’ and 3’ end.A single strand of DNA has a 5’ and 3’ end.

3’ end:3’ end: Terminates with Terminates with

an exposed –OH group onan exposed –OH group on

deoxyribose sugardeoxyribose sugar

5’ end:5’ end: Terminates with Terminates with

an exposed phosphatean exposed phosphate

groupgroup

What is the structure of DNA?What is the structure of DNA?

Antiparallel strandsAntiparallel strands- Single strands of DNA run opposite to one - Single strands of DNA run opposite to one another in the double-helix.another in the double-helix.

What is the structure of DNA?What is the structure of DNA?

Antiparallel strandsAntiparallel strands- Sequence of nucleotides is typically- Sequence of nucleotides is typicallywritten in the 5’ to 3’written in the 5’ to 3’direction.direction.

5’-ACTG-3’5’-ACTG-3’

Which is NOT the same as:Which is NOT the same as:

5’-GTCA-3’5’-GTCA-3’

Can you build your own DNA Can you build your own DNA model?model?