10/17/20151 DNA… THE BASIS FOR INHERITANCE

10/17/20152

3 I. SEARCH FOR GENETIC MATERIAL n A. EVIDENCE DNA CAN TRANSFORM BACTERIA –1. WHO: FREDERICK GRIFFITH 1928 –2. USED WHAT: 2 FORMS OF STREPTOCOCCUS PNEUMONIA

10/17/20154 STREPTOCOCCUS PNEUMONIA n a. S-STRAIN=SHINY SMOOTH COLONIES (WITH MUCOUS COAT) n b. R-STRAIN=ROUGH APPEARANCE (NO PROTECTIVE “COAT”)

10/17/20155 B. GRIFFITH’S 4 EXPERIMENTS n EXP. 1=INJECT LIVE S-STRAIN INTO MICE…MICE DEAD FROM PNEUMONIA

10/17/20156 EXPERIMENT 2 n INJECT LIVE R- STRAIN INTO MICE… MICE ALIVE…HARMLESS PNEUMONIA

10/17/20157 EXPERIMENT 3 n INJECT HEAT KILLED S- STRAIN INTO MICE. n HEAT KILLS BACTERIA, DESTROYS DNA n MICE DID NOT DEVELOP PNEUMONIA (MICE ALIVE)

10/17/20158 EXPERIMENT 4 n INJECT HEAT KILLED S- STRAIN AND LIVE R- STRAIN INTO MICE n EXPECTED LIVE MICE n GOT DEAD MICE

10/17/20159 n WHY?…LIVING R-STRAIN BACTERIA RECOVERED S- STRAIN GENETIC MATERIAL FOR MUCOUS COATS

10/17/ C. GRIFFITH CONCLUDED n TRANSFORMATION HAD OCCURRED n DEAD BACTERIA “SPILLS ITS GUTS” AND THE BACTERIA AROUND IT PICK UP THE DNA AND TAKE ON THE NEW TRAITS…INHERIT THOSE TRAITS

10/17/ D. OSWALD AVERY 1944 n WORKED IN VITRO, (IN GLASSWARE), TO EXTRACT DNA FROM S-STRAIN BACTERIA TO DEMONSTRATE THAT DNA WAS INDEED THE “TRANSFORMING” SUBSTANCE

10/17/ E. Alfred HERSHEY & Martha CHASE n 1. USED BACTERIOPHAGE (VIRUS WHICH INFECTS BACTERIA) BECAUSE IT CONTAINS ONLY DNA AND PROTEINS. n 2. EXP. STEP 1=VIRAL PROTEINS MARKED (SULFUR), DNA MARKED (PHOSPHORUS) IN 2 BATCHES OF PHAGES.

10/17/ n EXP. STEP 2= BACTERIOPHAGES INFECT E. coli n AFTER SEVERAL OTHER STEPS THE RESULTS WERE FOUND… PROTEIN WAS FOUND OUTSIDE THE E. coli AND THE PHOSPHORUS WAS FOUND INSIDE THE E. coli.

10/17/ n DNA WAS THE GENETIC MATERIAL BECAUSE IT WAS INSIDE THE CELL CAUSING PROTEIN SYNTHESIS

10/17/ F. BEADLE AND TATUM n 1.“ONE GENE=ONE POLYPEPTIDE” n 2.STUDIED NEUROSPORA(MOLD) n 3.X-RAYED THE MOLD CAUSING A DEFECT IN AN ENZYME PRODUCTION n 4.MOLDS WITH A SINGLE DEFECTIVE ENZYME HAD A SINGLE MUTATED GENE

10/17/ CONCLUSION OF EXP. n “ONE GENE=ONE POLYPEPTIDE” BECAUSE IF ONE PROTEIN (ENZYME) IS PRODUCED DEFECTIVELY IT WAS BECAUSE ONE GENE WAS MUTATED

10/17/ n GENE= A SEGMENT OF DNA WHICH CODES FOR ONE PROTEIN n THE ENTIRE DNA CODE IS NOT TRANSCRIBED AT ONCE, JUST THE PARTS NECESSARY!

10/17/ G. EDWIN CHARGAFF n 1. IN SPECIES HE STUDIED HE NOTED THAT C=G AND A=T REGULARILY n 2. THIS BECAME KNOWN AS CHARGAFF’S RULES

10/17/ H. X-RAY CRYSTALOGRAPHY n 1.ISOLATE DNA n 2.CRYSTALLIZE DNA n 3.X-RAY DNA ONTO FILM n 4.X-RAY BOUNCES OFF ATOMS TO GET A PATTERN OF SPOTS

10/17/ n 5.DARK EDGES WERE REPETITIONS (INSIDE THE MOLECULE, BASE PAIRS) n 6.”X” WAS HELICAL PORTION OF THE MOLECULE (OUTSIDE THE LADDER, SUGAR AND PHOSPHATE) n 7.R.FRANKLIN AND M.WILKINS INVOLVED IN THIS PROCESS