Effect of Temperature on the Activity of Catalase

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  • Topic: DNA, Gene, Base pair
  • Pages : 3 (508 words )
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  • Published : April 19, 2013
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DNA Structure
Monday, 15 April 2013 9:01 AM

- DNA = Deoxyribonucleic acid

DNA is a double-helix: it has two strands that twist around each other Each strand is made of single units call nucleotides It has a sugar-phosphate backbone Bases join the two strands by hydrogen bonds ○ These bases are cytosine, guanine, adenine and thymine. - Complementary base pairing is a key idea in genetics: C pairs with G, and T pairs with A. - Each strand of DNA can be millions of base pairs in length and is coiled up to make chromosomes. -

- Nucleotide:








- Adenine (A) Guanine (G)

Thymine (T) Cytosine

= Complementary base pairing rule

- A strands of nucleotides joined by covalent bonds

- The sequence of bases makes up the genetic code - These bases are 'read' in groups of three - These triplets are used to send instructions in the cell: to switch genes on and off, to make proteins and enzymes

Unit 3 Page 1


DNA is a double strand of polynucleotides The sugar-phosphate backbone is on the outside, the bases are on the inside The strand is held together by hydrogen bonds between the bases A only pairs with T. G only pairs with C. ○ This is called complementary base pairing - The two strands run in opposite directions ○ This is called anti-parallel - DNA twists into a double-helix, help by more hydrogen bonds. -

- Maintained structure ○ Hydrogen bonds hold adjacent sections together ○ Hydrogen bonds hold complementary base pairs together ○ Complementary base pairing ensures that mistakes are not made when copying or transcribing DNA ○ Sugar-phosphate backbone is hydrophilic so its positioned on the outside ○ Nitrogenous bases are very reactive so are protected on the inside ○ Polynucleotides are anti-parallel: they run in opposite directions

- Nucleosomes hold the DNA together to form the 'frame' of chromosomes: ○ Chromatins wrap around histone proteins and join to...
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