Maybe you know this …

All living things contain deoxyribonucleic acid (DNA).

DNA, in humans, is located in the nucleus of all of our cells.*

The DNA is arranged in the nucleus as organized packets known as chromosomes.

Packaging of DNAChromatin

Combination of DNA and proteinMass of very long fibres

ChromosomeOne long, condensed DNA moleculeContains hundreds or thousands of genes

DNA is wrapped tightly around proteins called histones

DNA and histone packages form structures resembling beads called nucleosomes

AMAZING DNA FACTS…AMAZING DNA FACTS…DNA from a single DNA from a single

human cell extends in a human cell extends in a single thread for almost single thread for almost 2 metres long!!!2 metres long!!!

we have about 50 trillion we have about 50 trillion cells, so DNA would stretch cells, so DNA would stretch to the sun not once, but …to the sun not once, but …

A HISTORY OF DNAA HISTORY OF DNA

Discovery of the DNA double helixDNA double helix

A. Friedrich Miescher – started investigating a compound he found in the nucleus of cells, called it “nuclein”

(1869)

B. Rosalind Franklin - X-ray photo of DNA.

(1952)

C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.(1953)

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. A ring-shaped sugar called

deoxyribose3. 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

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.

ACCTTGCCATTGGAACGGTA

Purines and Pyrimidines

G

G

A

T

T

A

A

C

T

G

C

A

T

C

Nucleotide Base pair

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

Preparing and Dividing DNAProcess of copying DNA molecule

called DNA replicationAfter replication and chromatin fibres

have condensed into chromatids, cell enters division

Each chromosome now consists of two identical joined copies called sister chromatids

Joined by a centromere

one chromosome

(unduplicated)

one chromosome(duplicated)

Centromere

Sister Chromatids

Telomere: protective end cap of chromosome