1. Question for Today: DNA is a polymer, which means that it is made up of many repeating single units called monomers. These monomers are called what? Nucleotides

3. DNA Structure DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix. A molecule of DNA is made up of millions of tiny subunits called Nucleotides. Each nucleotide consists of: 1. Phosphate group 2. Pentose sugar 3. Nitrogenous base

4. Nucleotides Phosphate Pentose Sugar Nitrogenous Base

5. James Watson & Francis Crick Used data of M.H.F. Wilkins and Rosalind Franklin, early 50’s Wilkins and Franklin studied the structure of DNA crystals using X-rays. The X pattern suggested the structure of DNA was a helix. Distance between the two “backbones” of DNA is constant along the length of the molecule

6. Used data of Erwin Chargaff, 1940’s and early 50's Chargaff’s Rule: His data showed that in each species, the percent of A equals the percent of T, and the percent of G equals the percent of C.

7. The Watson-Crick Model of the Structure of DNA DNA consists of two chains of nucleotides in a ladder-like structure which is twisted (Double Helix)

8. Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. The bases that make up the rungs of the ladder are attracted by a weak chemical bonds called hydrogen bonds There are four types of nitrogenous bases.

9. Nucleotides A Adenine T Thymine G Guanine C Cytosine

10. Nucleotides Each base will only bond with one other specific base Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Form a base pair.

11. Purine vs Pyrimidine Each of the four bases in DNA fall under the category of a purine or pyrimidine Purine Adenine Guanine Pyrimidine Cytosine Thymine A purine hydrogen bonds to the correspondong Pyrimidine

12. DNA Structure Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

13. G G A T T A A C T G C A T C

14. DNA Structure To crack the genetic code found in DNA we need to look at the sequence of bases. The bases are arranged in triplets called codons. A G G - C T C - A A G - T C C - T A G T C C - G A G - T T C - A G G - A T C

15. 10/24/2014 Question: Write the complementary strand of DNA using this template strand: 5’ A-T-C-A-G-T-C-G-T-A-C-G-T-A-C-T-G 3’ 3’ T-A-G-T-C-A-G-C-A-T-G-C-A-T-G-A-C 5’

16. DNA Structure A gene is a section of DNA that codes for a protein. Each unique gene has a unique sequence of bases. This unique sequence of bases will code for the production of a unique protein. It is these proteins and combination of proteins that give us a unique phenotype.

17. DNA Helicase-It unzips your Genes! DNA helicase is an enzyme that “unzips” the DNA during interphase This allows the DNA to replicate—or make a copy of itself Main function: to un-package an organism's genes

18. DNA Polymerase The DNA polymerases are enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA These enzymes are essential to DNA replication and usually work in pairs to create two identical DNA strands from a single original DNA molecule Goes to work after helicase “un-zips” the DNA!

20. Environment vs Gene Expression The expression of certain genes in an organism can be affected by the environment that the organism is in Temperature and pH, in addition to other variables, can affect the expression of a gene Why? Genes are coded for in the DNA and are by extension, proteins http://www.jostens.com/pause/pause_lp_pause _before_you_post.html