DNA StructureDNA Structure(“transforming (“transforming
principle”)principle”)
Human Human GeneticsGenetics
Chp. 9Chp. 9
A A gene is a long is a long section of a DNA section of a DNA molecule whose molecule whose sequence of sequence of building blocks building blocks specifies the specifies the sequence of sequence of amino acidsamino acids in a in a particular particular protein.protein.
GenesGenes combine combine to form to form amino amino acidsacids as letters as letters combine to form combine to form words.words.
Amino acidsAmino acids make make proteinsproteins
DNA StructureDNA Structure
DNA shape is a DNA shape is a double helixdouble helix
View from the sideView from the side Partially unwound double helix so you can see Partially unwound double helix so you can see
componentscomponents
DNA StructureDNA Structure
Views from the topViews from the topModel X-Ray
Photo-51
DNA composed of DNA composed of nucleotidesnucleotides
1.1. Sugar Sugar (deoxyribose)(deoxyribose)
2.2. Phosphate groupPhosphate group
3.3. Nitrogenous basesNitrogenous bases1.1. PurinesPurines
1.1. GuanineGuanine (G) (G)
2.2. Adenine Adenine (A)(A)
2.2. PyrimidinesPyrimidines1.1. CytosineCytosine (C) (C)
2.2. ThymineThymine (T) (T)
DNA Structure (Where DNA Structure (Where are they?)are they?)
A 5 C sugar and a A 5 C sugar and a phosphate group phosphate group form the backboneform the backbone
DNA is directionalDNA is directional AntiparallelismAntiparallelism
the head to tail the head to tail arrangement of the arrangement of the 2 entwined chains 2 entwined chains of DNA double of DNA double helixhelix
DNA StructureDNA Structure
DNA StructureDNA Structure
Nitrogenous Nitrogenous basesbases A, T, C, & GA, T, C, & G make up the make up the
rungs on the rungs on the ladderladder
Complementary Base Complementary Base PairingPairing
Bases held together Bases held together with Hydrogen bondswith Hydrogen bonds
Guanine pairs with Guanine pairs with CytosineCytosine Triple bondTriple bond
Adenine pairs with Adenine pairs with ThymineThymine Double bondDouble bond
Minor GrooveMinor GrooveMajor GrooveMajor Groove
binding binding proteins proteins interact with interact with DNA in the DNA in the major groove major groove b/c backbone b/c backbone isn’t in the wayisn’t in the way
DNA StructureDNA Structure
Chromosomes – not just DNA!Chromosomes – not just DNA! 1/3 DNA1/3 DNA Histone proteinsHistone proteins Other DNA binding proteinsOther DNA binding proteins also a small amount of RNA also a small amount of RNA
All together the chromosome All together the chromosome material is called material is called ChromatinChromatin
DNA StructureDNA Structure
A single A single molecule of molecule of DNA can be 1 DNA can be 1 in. longin. long
How does it fit How does it fit into a space into a space that is 1 that is 1 millionth that millionth that size?size?
HistonesHistones proteins that proteins that
DNA coils DNA coils aroundaround
DNA StructureDNA Structure3D Video Clip (Click next 4 times)
Nucleosome-Nucleosome- A unit of the A unit of the
chromatic structurechromatic structureDNA StructureDNA Structure
GREAT DIAGRAM (FIG. 9.11) ON PG 179Clicker ?’s 7-13
1.8 Histones 2.DNA 3.“linking”
histone
DNA Replication-DNA Replication-
Preserves genetic informationPreserves genetic information S phase of InterphaseS phase of Interphase Gives each new cell a complete set Gives each new cell a complete set
of of operating instructionsoperating instructions 5’ to 3’ direction only5’ to 3’ direction only 3 Hypothesized mechanisms for 3 Hypothesized mechanisms for
DNA ReplicationDNA Replication
?
DNA Replication (cont.)DNA Replication (cont.)SemiconservaSemiconserva
tivetiveConservativeConservative DispersiveDispersive
Each new Each new molecule molecule conserves half conserves half of the original of the original double helixdouble helix
One double One double helix specifies helix specifies creation of a creation of a second double second double helixhelix
Double helix Double helix shatters into shatters into pieces that pieces that then synthesize then synthesize new DNAnew DNA
Proved by Meselson and Stahl
Marked DNA with 14N
2nd generation DNA had ½ 14N and ½ 15N
Replication TechnologyReplication Technology
PCR- Polymerase Chain ReactionPCR- Polymerase Chain Reaction Uses DNA Polymerase to rapidly produce Uses DNA Polymerase to rapidly produce
millions of copies of a specific DNA millions of copies of a specific DNA sequence of interest.sequence of interest.
Perhaps the most successful technology Perhaps the most successful technology to ever emerge from LIFE SCIENCE!!!to ever emerge from LIFE SCIENCE!!!
Many UsesMany Uses Forensics- Forensics-
blood, convict, exonerate false accusationsblood, convict, exonerate false accusations Agriculture, Vet., Medicine, Env. Sci.,Agriculture, Vet., Medicine, Env. Sci.,
Microorganisms, viruses, parasites…Microorganisms, viruses, parasites…