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Higher Biology

Higher Biology . Unit 1: 1.1 Structure of DNA. Learning Intention. To expand knowledge of the structure of DNA. Success Criteria. Name the components of a nucleotide and identify them in a diagram Describe how the sugar phosphate backbone is created

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Higher Biology

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  1. Higher Biology Unit 1: 1.1 Structure of DNA

  2. Learning Intention • To expand knowledge of the structure of DNA

  3. Success Criteria • Name the components of a nucleotide and identify them in a diagram • Describe how the sugar phosphate backbone is created • Explain what is meant by a 3’ and 5’ end of DNA • Give the names of the 4 DNA bases • Name the type of bonds between the complementary bases

  4. From National 5… • On poster paper, in 3 minutes write/ draw as much as you can remember about DNA

  5. DNA • DNA stands for Deoxyribose Nucleic Acid. • It is as double stranded molecule made up of subunits called nucleotides. • Each nucleotide is made of 3 parts;- A base, a phosphate and a deoxyribose sugar (a sugar made of carbon, hydrogen and oxygen)

  6. Structure of a Nucleotide

  7. These are the same thing…

  8. Structure of a nucleotide The Carbons which make up the sugar are numbered in this arrangement. Remember Carbon 1 is at the base and work clockwise from there.

  9. This is what a nucleotide looks like at the molecular level…

  10. Arrangement of Nucleotides in DNA Nucleotides bond together to form the sugar-phosphate backbone of the DNA molecule. This is due to chemical bonds between the phosphateof one nucleotide and the carbon 3 of another nucleotide. The type of bonding involved in a Covalent bonds, which are very strong.

  11. Double stranded As DNA is double stranded, there is 2 chains of nucleotides. This is described as having two anti-parallel chainsdue to the arrangement of the nucleotides. 1 Side of the helix’ nucleotides have carbon 5 at the top, the other side of the helix has the carbon 5 at the bottom of the nucleotide.

  12. Essentially the nucleotide is flipped over on one side of the backbone.

  13. 3’ and 5’ • When we are discussing which Carbons are at the top of the nucleotide, we use the term “Prime”. • This is written as either 3’ or 5’. • 5’ is the strand which has the 5thCarbonat the top of the nucleotide • 3’ is the strand which has the 3rd Carbon at the top of the nucleotide. • So in a molecule of DNA, there is always a 5’ strand and a 3’ strand.

  14. The Code • There are 4 different types of base in DNA. • Thymine = T • Adenine = A • Guanine = G • Cytosine = C • They have complementarybase pairing • T pairs with A • G pairs with C

  15. Hydrogen Bonds • Holding the bases together are WEAK hydrogen bonds between the respective bases. Hydrogen bonds C and G 3 bonds T and A 2 bonds

  16. Success Criteria • Name the components of a nucleotide and identify them in a diagram • Describe how the sugar phosphate backbone is created • Explain what is meant by a 3’ and 5’ end of DNA • Give the names of the 4 DNA bases • Name the type of bonds between the complementary bases

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