2. 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.

3. Packaging of DNA Chromatin Combination of DNA and protein Mass of very long fibres Chromosome One long, condensed DNA molecule Contains hundreds or thousands of genes

5. DNA is wrapped tightly around proteins called histones DNA and histone packages form structures resembling beads called nucleosomes

6. AMAZING DNA FACTS… DNA from a single human cell extends in a single thread for almost 2 metres long!!! DNA from a single human cell extends in a single thread for almost 2 metres long!!! we have about 50 trillion cells, so DNA would stretch to the sun not once, but … we have about 50 trillion cells, so DNA would stretch to the sun not once, but …

7. A HISTORY OF DNA DNA double helix Discovery of the DNA 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)

8. DNA Structure DNA 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 group 2. A ring-shaped sugar called deoxyribose 3. Nitrogenous base

9. Nucleotides Phosphate Pentose Sugar Nitrogenous Base

10. Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. There are four types of nitrogenous bases.

11. Nucleotides A Adenine T Thymine G Guanine C Cytosine

12. Nucleotides Each base will only bond with one other specific base. Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Form a base pair.

14. DNA Structure Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand. ACCTTGCCAT TGGAACGGTA

15. Purines and Pyrimidines

16. G G A T T A A C T G C A T C

17. NucleotideBase pair

18. DNA Structure A 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.

19. Protein DNA Gene Trait

20. Preparing and Dividing DNA Process of copying DNA molecule called DNA replication After 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

21. one chromosome (unduplicated) one chromosome (duplicated) Centromere Sister Chromatids Telomere: protective end cap of chromosome