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SURVEY OF BIOCHEMISTRY Nucleic Acids

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Presentation on theme: "SURVEY OF BIOCHEMISTRY Nucleic Acids"— Presentation transcript:

1 SURVEY OF BIOCHEMISTRY Nucleic Acids

2 Which statement is INCORRECT?
PRS Question Which statement is INCORRECT? B-DNA is double helical In DNA, two H-bonds form between adenine and thymine In DNA, molar amounts of A+T = molar amounts of G+C DNA strands run antiparallel to each other

3 Which is not found in DNA?
PRS Question Which is not found in DNA? Thymine 2’-OH on pentose 3’-OH on pentose Phosphodiester bond

4 The link between the adenine base and the ribose sugar occurs:
PRS Question The link between the adenine base and the ribose sugar occurs: From N1 of A to the C1’ of ribose From N3 of A to the C1’ of ribose From N7 of A to the C1’ of ribose From N9 of A to the C1’ of ribose

5 Basics of Nucleic Acid Structure Supercoiling & Topoisomerases
RNA Structure Recombinant DNA Technology

6 Limitations to DNA Flexibility
Glycosidic Bond Sugar Pucker Sugar-Phosphate Backbone What is a torsion angle and how does it play a role in biomolecular structure?

7 Rotational Degrees of Freedom
Glycosidic Bond Only 2 permissible conformations of base: syn or anti

8 Glycosidic Bond Conformations
“Anti” conformation is most stable in B-DNA and A-DNA

9 B-DNA has a C2’-endo conformation…
Sugar Pucker B-DNA has a C2’-endo conformation…

10 A-DNA has a C3’-endo conformation…
Sugar Pucker A-DNA has a C3’-endo conformation…

11 DNA Supercoiling Increasing supercoiling

12 DNA Supercoiling L = T + W Linking Number (L)
Number of times one strand crosses another strand Here the red strand of DNA crosses the blue strand of DNA 10 times L = 10

13 DNA Supercoiling L = T + W Twist (T)
Number of times one strand makes a complete revolution about the helical axis. Here the red strand of DNA makes 10 revolutions about the helical axis T = 10

14 DNA Supercoiling L = T + W Writhe (W)
Number of times a duplex makes a complete revolution about itself. Counterclockwise turns are negative Clockwise turns are positive W = 0

15 Where do we observe supercoiling of DNA?

16 Topoisomerases Topoisomerases are enzymes that cleave DNA, thereby relieving supercoiling tension. Type 1A: ss breaks Type 1B: ss breaks Type 2: ds breaks

17 Types of RNA Messenger RNA - carries genetic information for protein synthesis Transfer RNA - covalently binds amino acids corresponding to its anticodon sequence Ribosomal RNA - RNA molecules that play a role in protein synthesis in conjugate with ribosomal proteins

18 Transfer RNA Structures
Carnegie Mellon U. NIH

19 Ribosomal RNA Structures
Frog 5S rRNA Subunit

20 Recombinant DNA Technology
Goal: Introduce foreign gene into a host organism Reproduction of the gene or gene product Function of the new gene product on the host Players: Gene insert, host, vector used to carry gene into host

21 Gene Insert Genomic DNA cDNA PCR
All of the DNA carrying genetic information for normal functioning of an organism cDNA DNA copied from mRNA PCR DNA that has been copied from a template in a polymerase chain reaction

22 What is Polymerase Chain Reaction (PCR)?
In vitro DNA synthesis Components include: Heat-stable DNA polymerase (Taq polymerase) Two Primers (DNA oligonucleotides) Deoxynucleotides –dATP, dTTP, dCTP, dGTP DNA template Mg++, buffer components, and water

23 How does PCR work? One PCR Cycle:


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