Structure of DNA (Most slides should be a review you NEED to have the underlined text in notes along with drawings that I say put in notes )

DNA is found in the nucleus of a cell. DNA is wrapped tightly to form chromosomes. DNA is made up of repeating units called nucleotides. Nucleotides = sugar & phosphate backbone, & nitrogenous bases pairs (A,T,G,C).

DNA Info...... Each cell has about 2 m of DNA The average human has 75 trillion cells The average human has enough DNA to go from the earth to the sun more than 400 times DNA has a diameter of only .000000002m

Function of DNA…… Storage of genetic information Self-duplication & inheritance Expression of the genetic message DNA’s major function is to code for proteins Information is encoded in the order of the nitrogenous bases

Structure of DNA…… 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: Phosphate group Pentose sugar Nitrogenous base

Nucleotides…… Phosphate Nitrogenous Base ( A, T, G, C ) Pentose Sugar

The phosphate and sugar form the backbone of the DNA molecule, whereas the nitrogenous bases form the “rungs” There are four types of nitrogenous bases: A, T, G, C

A Adenine T Thymine C Cytosine G Guanine

Nitrogenous Bases…… Double ring PURINES Adenine (A) Guanine (G) Single ring PYRIMIDINES Thymine (T) Cytosine (C) G A . T C

Base Pairing Rules: Purines only pair with Pyrimidines Hydrogen bonds are extremely weak but the millions of H-bonds together represent an extremely strong force that keeps the two DNA strands together C G 3 H-bonds T A 2 H-bonds

Sugar / Phosphate backbone Nitrogenous Bases P P S S S S S T A P P P Hydrogen bonds S S S S S S C G P P P P S S S S S S G C P P P P S S S S S S S A T Nucleotide

All the pieces of DNA…… P P S – A ~ T – S P P S – G ~ C – S S – T ~ A – S S – C ~ G –S ~ = Hydrogen bonds Double helix (twisted ladder) Backbone = Phosphate (P) Sugar (S) Rungs = nitrogenous bases (A,G,T,C) Purines = Adenine & Guanine Pyrimidines = Thymine & Cytosine Base pairing rule = A – T or T – A G – C or C - G

DNA Replication

Cell Division and DNA Replication… Cells divide for: . Growth, Repair, Replacement Before cells divide they have to double cell structures, organelles and their genetic information

DNA Replication: A – T and G – C OR T – A and C – G DNA must be copied before a cell divides The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing: A – T and G – C OR T – A and C – G Each strand of the original DNA serves as a template (or pattern) for the new strand

Replication Basics: DNA is unwound and is unzipped by helicase = enzyme 2 new complementary strands are made; DNA polymerase = enzyme that copies DNA The original strand is the template for the new strands made

1) Unzipping… Begins at Origins of Replication Two strands open forming Replication Forks (Y-shaped region) New strands grow at the forks Replication Fork Parental DNA Molecule 3’ 5’

As the 2 DNA strands open at the origin, Replication Bubbles form:

More Unzipping… The enzyme Helicase unzips and separates the 2 DNA strands by breaking the weak hydrogen bonds

. 2) DNA Polymerase… DNA polymerase binds to the strand of the DNA and begins adding nucleotides using the original DNA strand as a template

3) Original → New DNA DNA Template Parental DNA New DNA New DNA DRAW THIS IN YOUR NOTES DNA Template New DNA Parental DNA New DNA DNA Template

A ~ T C ~ G T ~ A A T C G T A A ~ T T ~ A ALSO DRAW THIS IN YOUR NOTES Unzips (by helicase) A ~ T C ~ G T ~ A New Strand (by DNA polymerase)

A C T G G A T Because of the complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand C

DNA → Genetic Code A G G – C T C – A A G – T C C – T A G To crack the genetic code found in DNA we need to look at the sequence of the nitrogenous bases The bases are arranged in triplets called codons Parent Strand 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 New Strand codon

Gene → trait… A gene is a section of DNA that codes for a protein Each unique gene has a unique sequence of nitrogenous 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 our unique traits

Gene Protein Trait

Central Dogma… DNA RNA Amino Acids Protein Traits

http://www.youtube.com/watch?v=_Q2Ba2cFAew&feature=related http://www.youtube.com/watch?v=AGUuX4PGlCc&feature=related