2.6 Structure of DNA & RNA - PowerPoint Presentation

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2.6 Structure of DNA & RNASlide2

2.6 Structure of DNA & RNA

Understandings:

The nucleic acids DNA & RNA are polymers of nucleotides.

DNA differs from RNA in the # of strands normally present, the base composition & type of pentose.DNA is a double helix made of 2 antiparallel strands of nucleotides linked by H bonding between complementary base pairs.

Nature of Science:Using models as representation of the real world: Crick & Watson used model-making to discover the structure of DNA.

Applications:Watson & Crick’s elucidation of the structure of DNA using model-making.

Skills:

Drawing simple diagrams of the structure of single nucleotides & of DNA & RNA, using circles, pentagons & rectangles to represent phosphates,

pentoses

& bases. Slide3
Understanding: Nucleic acids DNA & RNA are polymers of nucleotides.

Nucleic

= first discovered in the nucleus

Acid

= phosphate group is acidic, making overall DNA molecule acidicPolymer = large molecule made up of repeating subunitsMonomer = the repeating subunits or building blocks of a polymerAnalogy: If a polymer is a train, what is the monomer?

If a polymer is a pearl necklace, what is the monomer?Now it’s your turn to come up with an analogy…Slide4
Nucleic acids DNA & RNA are polymers of nucleotides.

DNA = deoxyribonucleic acid

RNA = ribonucleic acid

Nucleotide

= sugar + phosphate + N baseSlide5
Nucleotide

Sugar = pentose (5-C sugar)DeoxyriboseRiboseSlide6
Nucleotide

Phosphate group

Acidic

Negatively charged

Phosphoric acid Phosphate group Slide7
Nucleotide

Nitrogen base = nitrogenous base = base

Contains N

Ring-structure (single or double ring)

Basic (alkaline)Slide8
Nucleotide vs

nucleoside Slide9
Bonds in a DNA moleculeSlide10
Understanding:

DNA differs from RNA in # of strands normally present, base composition & type of pentose.

DNA

Sugar = deoxyribose

Double-stranded = 2 polymers of nucleotides4 bases = A, C, G, T

RNASugar = ribose

Single-stranded = 1 polymer of nucleotides4 bases = A, C, G, USlide11
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Skill: Drawing DNA & RNA moleculesSlide13
Understanding

: DNA is a double helix made of 2 antiparallel strands of nucleotides linked by H bonding between complementary base pairs.

Each strand is a chain of

nucleotides

, linked by covalent bonds.Antiparallel strands = run in opposite directions (5’ to 3’ and 3’ to 5’)

Double helix = 2 strands form a helical structure by winding together Complementary base pairing * A always H-bonds with T * C always H-bonds with GSlide14

Nature of Science: Using models as representation of the real world: Crick & Watson used model-making to discover the structure of DNA.

Model = Latin “modus” = “manner or method”

Originally architect’s plans

Molecular models are 3-DMolecular models help discover what structure of molecule isMade to be testedCan be rejected and replacedModels played role in Watson and Crick’s discovery of double helix in 1953Slide15
Watson and CrickSlide16
Watson & Crick did not “discover” DNA

Watson and Crick were the

first scientists to formulate an accurate description of this molecule's complex, double-helical

structure

. Built upon discoveries of Friedrich Miescher (1869), Phoebus Levene, and Erwin Chargaff, Maurice Wilkins & Rosalind Franklin.http://www.nature.com/scitable/topicpage/discovery-of-dna-structure-and-function-watson-397Slide17
Application: Crick and Watson’s discovery of the structure of DNA using model-making

1

st

model

Triple helixBases on outsideMg holds 2 strands togetherProblems: Would not be enough Mg (Franklin)Amount of A didn’t equal T; C didn’t equal G (Chargaff)2nd

modelA = T; C = GAntiparallel strandsComplementary base pairing allowed for replicationGenetic code = triplets of basesSlide18
TOK: What is the role of collaboration vs competition in scientific research?

http://www.youtube.com/watch?v=8kK2zwjRV0M