2. Died in 2004 Watson and Crick described the structure of DNA: 1953

3. Nucleic Acids are: DNA (deoxyribonucleic acid): - giant polymers that carry instructions for making proteins RNA (ribonucleic acid): -interpret and carry out the instructions coded in the DNA

4. Nucleic acids store the information to make proteins

5. Monomers of nucleic acids: nucleotides A nucleotide consists of a: Nitrogenous base Pentose sugar Phosphate

6. DNA Deoxyribose Ribose Sugars in: RNA

7. Many nucleotides in DNA :

8. Two nucleotides join together to form a dinucleotide and many form a polynucleotide

9. DNA is like a ladder Bases are like the rungs of the ladder.

10. Backbones of RNA and DNA consist of: alternating sugars and phosphates Bases: -are attached to sugars -project from the side

11. 5´ 3´ 5´ T G C T T T C G A C T G T T G A C G A A G C G T A A C A C A T A G C G C A T TA C G G A T T A C G T A A T C G A T Cartoon of base pairing Cartoon of double helix DNA is a double helix. A DNA molecule: consists of two polynucleotide strands each coiled in a right-handed helix (cylindrical spiral)

12. The two complementary polynucleotide strands are held together by hydrogen bonding between the nitrogenous bases of adjacent nucleotides

13. Complementary base pairing:  particular bases pair only with certain bases e.g. adenine – thymine  makes it possible to copy DNA molecules faithfully

14. Chargaff’s rule: A+G = T+C e.g. If there is 31% adenine in DNA, find the percentage of guanine. A = T = 31 + 31 = 62%. So C + G = 100 – 62 = 38%. Guanine = 38/2 = 19%

15. The virus has single-stranded DNA as its genetic material. Explain the evidence from the table which suggests that the DNA is single-stranded. (2) Organism Percentage of each base AdenineGuanineCytosineThymine Human31.218.8 31.2 Cow27.922.1 27.9 Salmon29.420.6 29.4 Rat28.6 21.4 28.6 Virus24.724.118.532.7 amounts of A and T /C and G/complementary bases different; therefore no base-pairing;

16. Differences between RNA & DNA

17. RNADNA pentose sugar: ribose pentose sugar: deoxyribose bases: adenine, guanine, cytosine uracil bases: adenine guanine cytosine thymine

18. RNADNA ratio of: adenine & uracil to cytosine & guanine varies ratio of: adenine & thymine to cytosine & guanine is one

19. RNADNA manufactures in the nucleus but found throughout the cell found almost entirely in the nucleus [occurs in mitochondria & chloroplasts] interpret and carry out the instructions coded in the DNA carry instructions for making proteins

20. RNADNA RNA strands are continually made, broken down and reused DNA is completely protected by the body

21. RNADNA RNA is synthesized from DNA when needed DNA is self-replicating

22. RNADNA maybe temporary - existing for short periods permanent 3 basic forms: messenger, transfer and ribosomal RNA only one basic form

23. THE END