Structure of Nucleotide www assignmentpoint com Structure of

Structure of Nucleotide www. assignmentpoint. com

Structure of a nucleotide A nucleotide is made of 3 components: u A Pentose sugar u This is a 5 carbon sugar u The sugar in DNA is deoxyribose. u The sugar in RNA is ribose. www. assignmentpoint. com

Structure of a nucleotide A Phosphate group u Phosphate groups are important because they link the sugar on one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide. u www. assignmentpoint. com

Structure of a nucleotide u A Nitogenous base u In DNA the four bases are: – – u Thymine Adenine Cytosine Guanine In RNA the four bases are: – – Uracil Adenine Cytosine Guanine www. assignmentpoint. com

Nitrogenous bases – Two types Pyramidines Purines Thymine - T Cytosine - C Uracil - U Adenine - A Guanine - G www. assignmentpoint. com

Adenine www. assignmentpoint. com

Guanine www. assignmentpoint. com

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Sugar phosphate bonds (backbone of DNA) Nucleotides are connected to each other via the phosphate on one nucleotide and the sugar on the next nucleotide u A Polynucleotide u www. assignmentpoint. com

James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA www. assignmentpoint. com

X-ray diffraction photograph of the DNA double helix www. assignmentpoint. com

Base pairing u The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA. www. assignmentpoint. com

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The Rule: u Adenine always base pairs with Thymine (or Uracil if RNA) u Cytosine Guanine. always base pairs with u This is beacuse there is exactly enough room for one purine and one pyramide base between the two polynucleotide strands of DNA. www. assignmentpoint. com

Complementary base pairing Purines Pyramidines Adenine Thymine Uracil Guanine Cytosine www. assignmentpoint. com