DNA Structure (“transforming principle”) Human Genetics Chp. 9

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


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



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


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


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…

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DNA Structure (“transforming principle”) Human Genetics Chp. 9