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”