7.012_Section_2-solution_key_-2010

7.012_Section_2-solution_key_-2010 - 1 Solution key 7.012...

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Unformatted text preview: 1 Solution key - 7.012 Recitation 2 - 2010 Questions : 1. Nucleic acids are of two major types: double helical DNA and single stranded RNA. i. Draw the chemical structure of a DNA molecule composed of three deoxy-ribonucleotides. Label the 3’ and 5’ ends. ii. How is a nucleotide different from a nucleoside? A nucleoside is comprised of a nucleic acid base (A, T, G, C, U) and ribose/deoxyribose sugar. In comparison, the nucleotide has a base and a 5 carbon sugar that has the phosphate groups. iii. Why the two strands of DNA are anti-parallel to each other? The anti-parallel arrangement of the two strands in a DNA duplex allows the complementary bases to stack in a manner that allows them to hydrogen bond with each other. This arrangement also ensures that both the strands replicate in a 5’ → 3’ direction (you will learn more about this in your Molecular biology lectures). iv. Why is RNA more reactive compared to a DNA? The extra –OH group at the 2’C of the ribose sugar allows RNA to be more reactive compared to DNA. v. RNA is single stranded. However, it can have a very complex three-dimensional structure. Certain regions of RNA may show intra- molecular base pairing. Is the base pairing observed in RNA similar to or different from that in DNA? Yes, the intra-molecular base pairing in RNA follows the same complementary base-pairing rule as DNA where A forms two hydrogen bonds with U and C forms three hydrogen bonds with G. A forms two hydrogen bonds with U and C forms three hydrogen bonds with G....
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This note was uploaded on 03/12/2011 for the course BIO 7.012 taught by Professor Lander during the Fall '10 term at MIT.

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7.012_Section_2-solution_key_-2010 - 1 Solution key 7.012...

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