Chapter 12: DNA Mr. Freidhoff

1900’s What is known to man? – Chromosomes carry genetic information. – Some type of heredity is passed on to offspring. – Chromosomes consist of DNA. Not sure if Proteins or DNA regulate life.

Griffith Experiment Griffith was working with bacteria that caused pneumonia. S (Smooth) strain of bacteria would kill the mouse. R (Rough) strain would not kill the mouse.

Griffith Experiment Boiled S strain, killing the cells. Injected boiled S strain into the mouse and the mouse was ok!

Griffith Experiment Mixed boiled S strain and R strain and injected it into the mouse. Killed the mouse. Hypothesis: There is some kind of chemical substance that isn’t alive that is capable of transforming a cell. – Called this transformation.

Hershey and Chase Experiments Martha Chase Alfred Hershey

Bacteriaphage Video

Could proteins be the blueprint for life? Labeled outside of virus (protein) with radioactive isotope. New Viruses were not radioactive. – Was not the code for life. Could DNA be the blueprint of life? Labeled DNA with radioactive isotope. New Viruses were radioactive. – EVIDENCE!! – DNA is the blueprint of life!! Hershey and Chase Experiments

Hershey and Chase Experiment

Rosalind Franklin Ph.D in science. Worked on structure of DNA. Took ”pictures” of DNA. Took Photograph 51. Work was “used” when analyzing structure of DNA. Never awarded noble prize.

Rosalind Franklin

X-ray Diffraction Pattern of DNA “Photograph 51”

Watson and Crick Used data of Erwin Chargaff and Rosalind Franklin. Built DNA models from data. The X pattern suggested the structure of DNA was a helix Nobel Prize for Physiology and Medicine.

Watson and Crick

Watson & Crick Model DNA Structure

Who deserves the credit? Rosalind Franklin James Watson Francis Crick Maurice Wilkins

DNA D eoxyribo n ucleic A cid. Genetic information stored. Located in nucleus of the cell. Main Purpose: Blueprint for proteins. Single human cell contains more than 2 meters of DNA stretched out.

Nucleotides Made of three parts. 1)Phosphate Group. 2)Ring shaped sugar molecule: Deoxyribose. 3)Nitrogenous Base: Single or Double Ring. Phosphate Group Pentose Sugar Nitrogenous Base

Nucleotides Nucleotides (monomers) are the building blocks of DNA (polymers). 4 different types in nucleotides. – Adenine (A) – Guanine (G) – Thymine (T) – Cytosine (C)

Pyrimidines and Purines Pyrimidines: Single ring nucleotide. – Cytosine – Thymine (DNA Only) – Uracil (RNA Only) Purines: Double ring nucleotide. – Adenine – Guanine

G G A T T A A C T G C A T C Each purine bonds with a specific pyrimidine. A bonds with T. G bonds with C.

Replication Practice DNA AGCTTAGCATTGGACCT TCGAATCGTAACCTGGA

Structure of DNA DNA consists of two chains of nucleotides in a twisted ladder structure (Double Helix). Nucleotides connected by covalent bonds going up each side. Every turn on the DNA has 10 nucleotides. Sugar-phosphate Backbone. – Sides of DNA – Support for nitrogen bases. Video

Hydrogen bonds between bases hold the strands together Ribbon modelPartial chemical structureComputer model Hydrogen bond

A and T: Double Hydrogen Bond G and C: Triple Hydrogen Bond

Nucleotides  DNA DNA is made up of many nucleotides. Chromosomes have millions of nucleotides. Human Genome is over 3 BILLION base pairs long.

DNA by the Numbers Each cell has about 2m 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. The earth is 150 billion m or 93 million miles from the sun.

Chargaff’s Rule Erwin Chargaff discovered : Percent of A approximately equals T. Percent of G approximately equals C. This is true for all species!

Question 1 You find a new type of bacteria and sequence the genome and find the percentage of thymine is 21%, what is the percentage of adenine? 21%

Question 2 A geneticist sequences the genome of a lion and finds the percentage of guanine is 34%, what is the percentage of adenine? 16%

DNA Replication Mr. Freidhoff

Cell Division When a cell divides, the new cell needs a copy of the genetic information. – Occurs during S phase. DNA Replication: Process of producing two identical replicas from one original DNA. molecule.

DNA Replication Each strand of DNA acts as a ‘negative’ for producing a new complimentary strand. Same base pairing as before.

DNA Replication DNA replication starts at sites called replication fork. Enzyme helicase unzips the DNA molecule. – Breaks the hydrogen bonds. Video

DNA Replication and Structure Two sides of DNA are different. – Run antiparallel. One end is known as the 5’ end while the other is known as the 3’ end. 5’ end is phosphate. 3’ end is sugar.

DNA Replication and Structure Leading Strand. – Moves the same direction of the replication fork. Lagging Strand. – Runs opposite direction. – Creates Okazaki fragments.

DNA Polymerase An enzyme that catalyzes the addition of a nucleotide to the growing DNA chain. – Assembles free floating nucleotides into complementary strands of DNA.

DNA Polymerase Usually work in pairs. Also proofreads each new strand of DNA to check for mistakes. Adds nucleotides onto the 3’ end.

DNA Polymerase