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2. DNA stands for deoxyribose nucleic acid This chemical substance is present in the nucleus of all cells in all living organisms DNA controls all the chemical reactions which take place in cells The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA DNA 2

3. DNA is a very large molecule made up of a long chain of sub-units The sub-units are called nucleotides Each nucleotide is made up of a sugar called deoxyribose a phosphate group -PO 4 and an organic base DNA molecule 3

4. Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule Deoxyribose is almost the same but lacks one oxygen atom Both molecules may be represented by the symbol Ribose & deoxyribose 4

5. The four organic bases are Adenine(A) Thymine(T) Cytosine(C) Guanine (G) The bases 5

6. The deoxyribose,the phosphateand one of the bases adenine deoxyribose PO 4 Combine to form a nucleotide Nucleotides 6

7. A molecule of DNA is formed by millions of nucleotides joined together in a long chain PO 4 sugar-phosphate backbone + bases Joined nucleotides 7

8. DNA consists of a double strand of nucleotides The sugar-phosphate chains are on the outside and the strands are held together by chemical bonds between the bases 8

9. PO 4 2-stranded DNA 9

10. The bases always pair up in the same way Adenine forms a bond with Thymine and Cytosine bonds with Guanine Bonding 1 10 AdenineThymine Cytosine Guanine

11. PO 4 thymine PO 4 adenine cytosine PO 4 guanine Bonding 2 11

12. The paired strands are coiled into a spiral called A DOUBLE HELIX 13

13. sugar-phosphate chain bases THE DOUBLE HELIX 14

14. How do we REPLICATE DNA? DNA double helix unwinds DNA now single-stranded New DNA strand forms using complementary base pairing (A-T, C-G) Used to prepare DNA for cell division Whole genome copied/replicated This is called COMPLIMENTARY PAIRING

15. DNA unwinds

16. New DNA strand forms using complementary base pairing (A-T, C-G)

17. LETS PRACTICE  Write the COMPLIMENTARY DNA strand using the DNA base pairing rule  A C G A T A T C G A A T C G C A

18. The SEQUENCE of bases in DNA forms the Genetic Code A group of three bases controls the production of a particular amino acid in the cytoplasm of the cell The different amino acids and the order in which they are joined up determines the sort of protein being produced Genetic code 1 19

19. Questions to be answered..  How do we get from the bases found in DNA to amino acids?  How do we get from a bunch of amino acids to proteins?

20. How do we make proteins from DNA?  DNA are the instruction booklet for how proteins are made  DNA must go through two processes : TRANSCRIPTION AND TRANSLATION

21. Protein Structure Review  Made up of amino acids  Polypeptide- string of amino acids  20 amino acids are arranged in different orders to make a variety of proteins  Made in the RIBOSOMES (Protein factories)

22. DNA RNA Protein

23. MAKING A PROTEIN  STEP 1: TRANSCRIPTION  STEP 2: TRANSLATION

24. 1 st Process: TRANSCRIPTION  Transcription: Making a strand of RNA

25. STEP ONE:  DNA double helix must unwind into two single strands. DNA double helix will unwind. This is done by the enzyme DNA HELICASE

26. Transcription  Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA (mRNA) by the enzyme RNA polymerase.  Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language.

27. Step Two: TRANSCRIPTION

28. Transcription  The enzyme RNA polymerase will come in and begin creating a strand of RNA based on DNA sequence  A  U  C  G Only difference: A now pairs with U (Uracil) instead of T (Thymine)

30. DNA vs RNA DNA is double stranded RNA is single stranded DNA contains Thymine RNA contains Uracil DNA is used to make RNA RNA is used to make a protein DNA is used in transcription RNA is used in translation

31. LETS PRACTICE  Create your RNA strand from this strand of DNA  A C G A T A T C G A A T C G C A

32. 2 nd Process: Translation Translation: Building our protein from amino acids

33. Protein Structure Review  Made up of amino acids  Polypeptide- string of amino acids  20 amino acids are arranged in different orders to make a variety of proteins  We will now create this chain of amino acids in TRANSLATION

36. Translation  Every THREE nucleotides in RNA is called a CODON  RNA is then coded into amino acids  Each codon codes for one amino acid

37. For example Cytosine Adenine Codes for Valine Cytosine (C) Guanine (G) Adenine (A) Codes for Alanine Uracil Coding 21

38. This is known as the triplet code Each triplet codes for a specific amino acid CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA - AlaValGly ArgProLeuGly AlaValGly ArgProLeuGly The amino acids are joined together in the correct sequence to make part of a protein Triplet code 22

39. Ser-Cyst-Val-Gly-Ser-Cyst Ala Val Val-Cyst-Ser-Ala-Ser-Cyst-Gly Val- Cyst-Ala-Ala-Ser-Gly This is a small, imaginary protein molecule showing how a sequence of 5 different amino acids could determine the shape and identity of the molecule Each amino acid ( Serine, Cysteine, Valine, Glycine and Alanine) is coded for by a particular triplet of bases Genetic code 2 20

40. The proteins build the cell structures They also make enzymes The DNA controls which enzymes are made and the enzymes determine what reactions take place The structures and reactions in the cell determine what sort of a cell it is and what its function is So DNA exerts its control through the enzymes DNA and enzymes 23