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Unformatted text preview: DNA and RNA Structure 1 Last Time
What is Molecular Biology? Fusion of genetics and biochemistry Molecular basis of how DNA is reproduced, expressed, structured A timeline of discoveries The RNA World hypothesis RNA was the ﬁrst informational molecule in life forms 2 DNA and RNA structure
DNA is the genetic material DNA and RNA components How DNA strands are held together Higher order structure How to read scientiﬁc articles 3 Deoxyribonucleic acid (DNA) is the genetic material
-Stores genetic information in the form of a code: a linear sequence of nucleotides. - Replicated by copying the strands
using each as a template for the production of the complementary strand.
http://addiandcassi.com/wordpress/wp-content/uploads/dna-image.jpg 4 What are the subunits that make up DNA? RNA? 5 DNA nucleotides are comprised of: deoxyribose
5’ 4’ 3’ 2’ 1’ nitrogenous base phosphoric acid Pyrimadine or Purine DEOXYRIBO NUCLEIC ACID 6 Nucleosides (of DNA) – Precursors to Nucleotides
Nucleoside Nucleoside = base + sugar sugar base sugar images.teamsugar.com .wikimedia.org 7 The 4 Nucleotides of DNA A G C T
8 for deoxynucleotides, add a ‘d’ in front of the abbreviation as in: AMP is a ribonucleotide dAMP is a deoxyribonucleotide (shown) 9 Molecular structure of RNA vs. DNA RNA DNA Ribose replaces deoxyribose; uracil replaces thymine
10 Molecular structure of RNA vs. DNA RNA DNA Ribose replaces deoxyribose; uracil replaces thymine
11 How are DNA and RNA molecules held together within a strand? 12 In DNA and RNA, nucleotides are held together by phosphodiester bonds. 5’ 4’ 3’ 2’ 1’ 13 What chemical forces hold the DNA strands together? 14 1. Hydrogen bonds between bases Fig 2.13
15 2. Van der Waals interactions between pairs of neighboring bases Evidence: Compounds that interfere with Hydrogen bonds (urea, formamide) don’t separate strands by themselves, still requires heat 16 3. Double-stranded helix structure also promoted by having phosphates on outside, interact with H2O and counter ions (K+, Mg2+, etc.)
Mg2+ + K+ + -+-- - + + H2O 17 Heating breaks bonds between strands of DNA = DNA denaturation (or melting) Fig. 2.14 18
18 DNA Melting Curve
When DNA melts, the 2 strands come apart, and its absorbance in the UV region increases. Fig. 2.17 Tm= temp. at which 50% of DNA is melted.
19 G-C content determines melting temperature: varies among organisms 20 Re-Annealing or Hybridization Works with: • DNA - DNA • DNA - RNA • RNA - RNA Basis of many techniques in molecular biology. Fig 2.20
21 Higher order structures of DNA and RNA 22 3 Ways of Depicting DNA Structure 23 Double-stranded DNA features
1. 2. 3. 4. Helix is right handed 10 base-pairs/turn 3.4 nm (34 angstroms)/turn Helix has a major groove and a minor groove. 24 DNA structures
A B Z Fig. 2.16
25 Higher Order RNA Structure
Stem-loops are common elements of RNA structure.
Stems are doublestranded regions of RNA that are A-form helices. They follow Watson-Crick base pairing rules. (DNA is typically a Bform helix). Stem loop 26 Secondary structure diagram Tertiary structure diagram rRNA intron rRNA intron
DNA is the genetic material Components Nucleosides and nucleotides Forces holding strands together : Hydrogen bonding Van der Waals forces Interaction with ionic solutions Measuring G-C content with absorbance Higher order structure different forms of DNA secondary and tertiary structures of RNA
28 29 What’s in a journal article? 30 Paper Bashing Exercise
• Big Question • Research Question • Methods Used • Conclusion 31 Paper Bashing Template Part I
• What is the Big Question? • provide some background • What is the Research/Paper Question? • Brieﬂy describe the methods used • What are the results and conclusion? 32 Paper Bashing Template Part II
• What question does the ﬁgure address? • What are the methods used? • explain in some detail • What do the data/results show? • What do you conclude from the data? • What is the authors’ conclusion? • Do they differ? Discuss. 33 Next Time
DNA Replication next 4 lectures Image courtesy: http://www.steve.gb.com 34 ...
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This note was uploaded on 04/10/2010 for the course BIO 51130 taught by Professor Moon during the Spring '09 term at University of Texas at Austin.
- Spring '09