Where do we get our DNA from?

Structure of DNADiscovered in 1950s by Rosalind

Franklin using X-ray diffraction.

“Double Helix” term coined by Watson and Crick in the 1950s as well.

DNA is arranged into a ladder-like structure called a Double Helix.

DNA Structure

A molecule of DNA is made up of millions of tiny subunits called Nucleotides.

Each nucleotide consists of:1. Phosphate group2. Pentose sugar3. Nitrogenous base

Nucleotides

Phosphate

Pentose

Sugar

Nitrogenous

Base

NucleotidesThe phosphate and sugar form the

backbone of the DNA molecule, whereas the bases form the “rungs”.

There are four types of nitrogenous bases.

Nucleotides (Practice)

A

Adenine(Purine)

T

Thymine(Pyrimidines)

G

Guanine(Purine)

C

Cytosine(Pyrimidines)

NucleotidesEach base will only bond with one

other specific base.

Adenine (A)Thymine (T)

Cytosine (C)Guanine (G)

Form a base pair.

Form a base pair.

DNA StructureBecause of this complementary base

pairing,

the order of the bases in one strand determines

the order of the bases in the other strand.

BASE PAIRING IS ALWAYS EQUAL!!!!(Ex: 25% A=25% T)

G

G

A

T

T

A

A

C

T

G

C

A

T

C

What do these have in common?

ALL organisms have the SAME components

that make up their DNA!

Think about the Alphabet...

DNA StructureA gene is a section of DNA that codes

for a protein.

Each unique gene has a unique sequence of bases.

This unique sequence of bases will code for the production of a unique protein.

It is these proteins and combination of proteins that give us a unique phenotype.

Protein

DNA

Gene

Trait

The purpose of DNA is to help the ribosomes make

PROTEIN!!!!

Write this down..

How are our traits carried on our DNA?

DNA is copied during a process called replication!

What phase of the cell cycle does DNA replication occur?

Replication results=one new strand & one original strand

http://www.youtube.com/watch?v=5_vzY7H9GYk&feature=related