DNA History and DNA Structure
Name Discovery Importance
Frederick Griffith
Oswald Averey, Colin MacLeod and Caclyn McCartyHershy and Chase
Chargaff
LeveneRolalind Franklin
Watson and Crick
How did we get here?? – Make a table using pages 204-212
DNA structure
Purines have two ringsPyrimidines have one ring
• DNA has four kinds of bases, A, T, C, and G
Figure 10.2B
Pyrimidines
Thymine (T) Cytosine (C)
Purines
Adenine (A) Guanine (G)
• James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin
DNA is a double-stranded helix
Figure 10.3A, B
• DNA is a nucleic acid, made of long chains of nucleotides
DNA and RNA are polymers of nucleotides
Figure 10.2A
Nucleotide
Phosphate group
Nitrogenous base
Sugar
Polynucleotide Sugar-phosphate backboneDNA nucleotide
Phosphategroup
Nitrogenous base(A, G, C, or T)
Thymine (T)
Sugar(deoxyribose)
• Hydrogen bonds between bases hold the strands together: A and T, C and G
Figure 10.3D
Ribbon model Partial chemical structure Computer model
Hydrogen bond
• Each strand of the double helix is oriented in the opposite direction
Figure 10.5B
5 end 3 end
3 end 5 end
P
P
P
PP
P
P
P
Figure 2.5 - 5’ end : Phosphate at carbon 5 is not bound to another nucleotide3’ end – carbon at position 3 is not joined to another nucleotide.
DNA structure
What is the complementary sequence to the following ?
5’ – ATG – 3’
Draw the complementary sequence. Include all the correct drawing of molecules, and the bonding between them. Consult your text book for help.
Read pages 215-218.
DNA structure
Packing of information
2 m of material in 4 uM
DNA associates with a family of proteins called histones
Histones form structures called nucleosomes
Condense further to ultimately form chromatin – Long intertwined strands of DNA.
During cell division threads of chromatin condense and become visible as distinct chromosomes
DNA structure
DNA super coiling: the formation of additional coils in the structure of DNA due to twisting forces on the molecules
DNA structure
What is a chromatid?What is a centromere?What is a chromomere?
Chromatid - one of the two copies of DNA making up a duplicated chromosome, which are joined at their centromeres.Centromere – a protein structure that links sister chromatidsChromomere - serially aligned beads or granules of eukaryotic chromosome resulting from local coiling.
http://learn.genetics.utah.edu/content/begin/dna/builddna/
Name Discovery Importance
Frederick Griffith Passing information from one cell to another
Cells can store information – the “transforming principle”
Oswald Averey, Colin MacLeod and Caclyn McCarty
DNA is where information is stored
Targeting the molecules of heredity
Hershy and Chase Confirmed that DNA was the molecule of interest
Focused scientists on DNA
Chargaff Nucleotides are present in certain proportions (A=T, C+G)
Provided insight for solving the structure of DNA.
Levene Isolated and named nucleic acids
Rolalind Franklin The structure of DNA Provides a framework for solving the structure
Watson and Crick Build the model Had properties consistent with ‘the molecular code for life”