ap biology 2006-2007 the discovery and structure of the genetic material called “dna”
TRANSCRIPT
AP Biology 2006-2007
The Discovery and Structure of The Genetic Material
called “DNA”
AP Biology
Frederick Griffith finds a “Transforming Factor”
“Transformation” something in heat-killed bacteria could still transmit disease-causing properties
live pathogenicstrain of bacteria
live non-pathogenicstrain of bacteria
mice die mice live
heat-killed pathogenic bacteria
mix heat-killed pathogenic & non-pathogenicbacteria
mice live mice die
A. B. C. D.
AP Biology
So what is this “transforming factor” Deoxyribonucleic Acid
or what we have been calling DNA every single organism on our planet has
its own DNA molecule “blueprint of life” why is it called this?
Franklin Wilkins Pauling
AP Biology
Watson and Crick
CrickWatson
Watson & Crick developed
double helix model of DNA
AP Biology
DNA is a Nucleic Acid • Nucleic Acids are made from Nucleotides• A Nucleotide has three parts:
1. phosphate group 2. sugar molecule (Deoxyribose)3. nitrogen-containing base (A,T,C,G)
phosphate group
nitrogen-containingbasesugar
You will have torecognize nucleotideshape on EOC!!!!!!
AP Biology
A closer look at the different nitrogen bases!
4 different nucleotides A – adenine T – thymine C – cytosine G - guanine
nucleotide – nucleotide – nucleotide – nucleotide
phosphate
sugar N base
AP Biology
Making the DNA Molecule
Base pairing rules: adenine (A) = thymine (T) “AT” guanine (G) = cytosine (C)
AP Biology
Don’t forget about the other nucleic acid RNA is different from DNA molecules
single strand of nucleotides sugar is ribose Thymine (T) is replaced with Uracil (U)
AP Biology Copying DNA
“DNA Replication”How do cells make
new DNA molecules?
AP Biology
Remember why DNA must be duplicated…
nucleus
cell
DNA in chromosomes
nucleus
cell
duplicated chromosomes
Cells divide so each cellneeds own copy of DNA
AP Biology
But how is DNA copied? Its called replication of
DNA DNA unzips and each
side serves as a template for a new strand
AP Biology
DNA Replication Step 1: DNA Strands “unzip” at the
weak bonds between bases Enzyme used - helicase
helicase
AP Biology
DNA Replication
DNA polymerase
Enzyme DNA polymerase adds new bases
DNA basesin nucleus
Step 2: Complementary strand is made
AP Biology
DNA Replication Result is 2 exact copies of DNA to split
between new cells
DNA polymerase
DNA polymerase
AP Biology
• DNA replication starts at many points in eukaryotic chromosomes.
• Called “replication bubbles”
Replication is fast and accurate.
AP Biology
DNAPolymerase
Copying DNA
Build daughter DNA strand direction opposite direction
anti-parallel- think divided highway
AP Biology
So lets sum it up