http://publications.nigms.nih.gov/thenewgenetics/chapter1.html

DNA StructureDNA consists of two molecules that are

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

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

http://i-biology.net/ahl/07-nucleic-acids-and-proteins/

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.

AnalogiesStrengths of

Ladder AnalogyWeaknesses ofLadder Analogy

• double-helix shape is well represented

• location of sugar-phosphate backbone is accurate

• location of nucleotides is accurate

• individual nucleotides (A, T, C, G) are not represented

• individual sugars and phosphates are not shown

• base pairing (A-T, C-G) is not represented

Nucleotides

A

Adenine

T

Thymine

G

Guanine

C

Cytosine

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.

http://1.bp.blogspot.com/_gWQaU40PH24/S7J-tYkvibI/AAAAAAAAGas/-_raVWK4zx4/s1600/dna%5B1%5D.gif

Complementary base pairingPurines Pyramidines

Adenine ThymineAdenine Uracil

Guanine Cytosine

G

G

A

T

T

A

A

C

T

G

C

A

T

C

DNA StructureTo crack the genetic code found in

DNA we need to look at the sequence of bases.

The bases are arranged in triplets called codons.

A G G - C T C - A A G - T C C - T A GT C C - G A G - T T C - A G G - A T C

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

Nature of the Genetic MaterialProperty 1 - it must contain, in a

stable form, information encoding the organism’s structure, function, development and reproduction

Property 2 - it must replicate accurately so progeny cells have the same genetic makeup

Property 3 - it must be capable of some variation (mutation) to permit evolution

Your TaskDraw a flow chart to

show how to get from:

http://207.207.4.198/pub/flash/24/menu.swfNova-Cracking the Code of LifeThe Structure of DNA