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DNA

Learn about the structure and function of DNA, how it replicates, and how it codes for proteins through transcription and translation processes.

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DNA

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  1. 1 DNA

  2. 2 DNA 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

  3. 3 DNA molecule 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 -PO4 and an organic base

  4. 4 Ribose & deoxyribose Riboseis 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

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

  6. 6 Nucleotides PO4 adenine deoxyribose The deoxyribose, the phosphate and one of the bases Combine to form a nucleotide

  7. Joined nucleotides PO4 PO4 PO4 PO4 sugar-phosphate backbone + bases 7 A molecule of DNA is formed by millions of nucleotides joined together in a long chain

  8. 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

  9. 2-stranded DNA PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 9

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

  11. 11 Bonding 2 PO4 PO4 thymine adenine PO4 PO4 cytosine guanine PO4 PO4 PO4 PO4

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

  13. 14 THE DOUBLE HELIX bases sugar-phosphate chain

  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. Genetic code 1 19 The SEQUENCE of bases in DNA forms the Genetic Code A group of three bases controlsthe 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

  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. 1st 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)

  29. 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 DNA vs RNA

  30. 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

  31. 2nd Process: Translation Translation: Building our protein from amino acids

  32. 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

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

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

  35. Triplet code 22 This is known as the triplet code Each triplet codes for a specific amino acid CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA - Ala Val Gly Gly Arg Pro Leu Gly The amino acids are joined together in the correct sequence to make part of a protein Ala Val Gly Gly Arg Pro Leu Gly

  36. Genetic code 2 Ser-Cyst-Val-Gly-Ser-Cyst Ala Val Val-Cyst-Ser-Ala-Ser-Cyst-Gly Val- Cyst-Ala-Ala-Ser-Gly 20 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

  37. 23 DNA and enzymes 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

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