MODERN GENETICS  WHO DISCOVERED THE STRUCTURE OF DNA?  EVERYONE SEEMS TO KNOW WATSON AND CRICK, BUT WHO IS THIS? 

MODERN GENETICS  T.H. MORGAN OFFERED FIRST EVIDENCE OF WHAT SUBSTANCE INSIDE LIVING THINGS CONTROLS THEIR TRAITS  LIKE MENDEL, THE TRICK TO BEING SUCCESSFUL LIED IN WORKING WITH AN ORGANISM THAT COULD GIVE MANY GENERATIONS QUICKLY!!  HENCE, FRUIT FLIES

MODERN GENETICS  T.H. MORGAN’S WORK LED TO THE FOLLOWING UNDERSTANDING:  CHROMOSOMES CONTROL SEX (GENDER)  SEX-LINKED TRAITS  GENE LINKAGE

MODERN GENETICS  SEX DETERMINATION AND CHROMOSOMES  A SPECIFIC PAIR OF CHROMOSOMES, KNOWN AS THE SEX CHROMOSOMES, DETERMINES THE GENDER OF ANY INDIVIDUAL

MODERN GENETICS  SEX-LINKED TRAITS  OBSERVE THE PEDIGREE CHART… WHAT PATTERN DO YOU NOTICE?

MODERN GENETICS  SEX-LINKED TRAITS  WHEN A TRAIT APPEARS TO BE DISPLAYED IN ONE GENDER MORE FREQUENTLY THEN ANOTHER, AND THE ONLY DIFFERENCE BETWEEN EACH GENDER IS THE SEX CHROMOSOMES; THE TRAIT MUST BE ASSOCIATED/LINKED TO THE SEX CHROMOSOMES  X-LINKAGE VS. Y-LINKAGE

MODERN GENETICS  EXAMPLES OF X-LINKED TRAITS:  RED-GREEN COLORBLINDNESS  HEMOPHILIA

MODERN GENETICS  GENE LINKAGE  IT WAS DISCOVERED THAT GENDER AND TRAITS AREN’T THE ONLY THINGS THAT CAN BE LINKED…  ANY PAIR OF TRAITS FOUND ON THE SAME CHROMOSOME ARE CONSIDERED LINKED  WHAT DATA WOULD SUGGEST THAT TRAITS ARE LINKED? *HERE’S A HINT 

MODERN GENETICS  IF GENES ARE LINKED, HOW CAN THEIR BE PEOPLE WITH BROWN HAIR AND BLUE EYES?  CROSSING OVER!!  EXCHANGE BETWEEN HOMOLOGOUS CHROMOSOMES DURING SYNAPSIS OF MEIOSIS

MODERN GENETICS  RANDOM QUESTION…  IN HUMANS, DOES HEIGHT OCCUR IN JUST TWO FORMS; TALL VERSUS SHORT?  HOW CAN WE EXPLAIN THE LARGE RANGE OF PHENOTYPES FOR HUMAN HEIGHT?  POLYGENIC INHERITANCE  MORE THAN ONE GENE CONTROLS THE SAME TRAIT, CREATING A LARGE NUMBER OF POSSIBLE PHENOTYPES

MODERN GENETICS  AFTER UNDERSTANDING ABOUT THE DIFFERENT PATTERNS OF INHERITANCE, THIS STILL LEFT AN UNANSWERED QUESTION…  WHAT WAS THE ACTUAL SUBSTANCE THAT CONTROLLED THESE TRAITS TO BEGIN WITH?

MODERN GENETICS  THE GREAT DEBATE – PROTEIN VS. DNA  BY THE EARLY 1900’S, SCIENCE HAD ALREADY LEARNED OF THE EXISTENCE OF CHROMOSOMES AND THAT THESE CHROMOSOMES WERE COMPOSED OF BOTH PROTEINS AND NUCLEIC ACIDS  LITTLE WAS KNOWN ABOUT NUCLEIC ACIDS, AND PROTEINS WERE WELL UNDERSTOOD AT THAT TIME  AS PROTEINS WERE FOUND TO EXIST IN EVERY SUBSTANCE INVOLVED IN TRAITS, THEY WERE THE FRONT-RUNNER FOR THE ACTUAL SUBSTANCE THAT CONTROLLED TRAITS

MODERN GENETICS  ENTER “THE MOUSE-KILLER”  SIR FREDERICK GRIFFITH

MODERN GENETICS  GRIFFITH’S EXPERIMENTS WEREN’T ENOUGH FOR THE SKEPTICS…BUT EVEN THE SKEPTICS COULDN’T DENY THE FINDINGS OF…

MODERN GENETICS  HERSHEY AND CHASE EXPERIMENT

MODERN GENETICS  ONCE IT WAS ESTABLISHED THAT DNA CONTROLLED TRAITS, THERE WAS A MAD RUSH TO FIND OUT THE STRUCTURE OF DNA…  WHY IN THE WORLD WOULD SCIENTISTS CARE SO MUCH ABOUT THE STRUCTURE OF DNA?  STRUCTURE DENOTES FUNCTION

MODERN GENETICS  WHILE SCIENTISTS FIGURED OUT THE BUILDING BLOCKS OF DNA, HOW THOSE BUILDING BLOCKS GOT PUT TOGETHER ELUDED THEM…

MODERN GENETICS  ENTER OUR HERO’S  WATSON AND CRICK  CREDITED WITH IDENTIFYING / DISCOVERING THE STRUCTURE OF DNA!!!

MODERN GENETICS  DNA’S STRUCTURE

MODERN GENETICS  DNA’S STRUCTURE DNA IS A DOUBLE HELIX (TWISTED LADDER) ADENINE ALWAYS PAIRS WITH THYMINE AND CYTOSINE ALWAYS PAIRS WITH GUANINE EXPLAINED THE IMMENSE COMPLEXITY OF TRAITS (HOW DOES IT LEAD TO COMPLEXITY?) UNEXPECTEDLY EXPLAINED WHY DNA CAN MAKE IDENTICAL COPIES OF ITSELF (IDENTICAL OFFSPRING)

MODERN GENETICS  DNA REPLICATION

MODERN GENETICS  LEARNING THE STRUCTURE OF DNA STILL LEFT AN UNANSWERED QUESTION…  HOW WAS DNA THE SUBSTANCE THAT CONTROLLED AN INDIVIDUAL’S TRAITS, IF PROTEINS WERE WHAT WERE PRESENT THAT ACTUALLY SEEMED TO CONTROL THE APPEARANCE OF THE TRAIT?  SOMEHOW, DNA HAD TO BE CONTROLLING THE SYNTHESIS OF PROTEINS…

MODERN GENETICS  WHERE IS DNA FOUND?  WHERE DOES PROTEIN SYNTHESIS TAKE PLACE?  DOES DNA EVER LEAVE THE NUCLEUS?  NO!!!  HOW CAN DNA BE USED TO MAKE PROTEINS IF IT NEVER GOES NEAR THE RIBOSOMES IN THE CYTOPLASM?

MODERN GENETICS  HOW CAN DNA BE USED TO MAKE PROTEINS IF IT NEVER GOES NEAR THE RIBOSOMES IN THE CYTOPLASM? (HINT - HOW CAN TWO PEOPLE COMMUNICATE WHO NEVER SEE EACH OTHER AND DON’T HAVE TELEPHONES?)  THEY CAN WRITE TO EACH OTHER…WHICH IS EXACTLY WHAT DNA DOES, IT WRITES A MESSAGE TO BE SENT TO THE RIBOSOMES…  ENTER OUR MESSENGER – RNA !!

MODERN GENETICS  RNA VS DNA

MODERN GENETICS  THE PROCESS OF DNA WRITING A MESSAGE IN THE FORM OF RNA IS CALLED:  DNA TRANSCRIPTION  DNA  mRNA  ALL WE HAVE IS A MESSAGE, WE HAVEN’T MADE A PROTEIN YET…WHERE DO PROTEINS GET MADE?  THE mRNA CAN GO VISIT THE RIBOSOME FACE TO FACE

MODERN GENETICS  THE RIBOSOME USES THE mRNA AS THE INSTRUCTIONS ON HOW TO MAKE A PROTEIN  WHAT IS THIS PROCESS OF MAKING A PROTEIN CALLED?  PROTEIN SYNTHESIS  WHAT DOES A PROTEIN LOOK LIKE?  A LONG CHAIN OF AMINO ACIDS  HOW DOES PROTEIN SYNTHESIS WORK?  THE mRNA TELLS THE RIBOSOME WHAT THE ORDER OF AMINO ACIDS SHOULD BE IN BUILDING A PROTEIN

MODERN GENETICS  PROTEINS ARE MADE UP OF AMINO ACIDS; STUDIES HAVE SHOWN THAT THERE ARE 20 DIFFERENT AMINO ACIDS…  THERE ARE ONLY 4 NITROGENOUS BASES IN mRNA; A, U, C, G…HOW CAN 4 LETTERS = 20 DIFFERENT BASES?

MODERN GENETICS

 I FORGOT TO TELL YOU…RIBOSOMES DON’T SPEAK PROTEIN (IN OTHER WORDS THEY DON’T KNOW WHAT AMINO ACID MATCHES A CODON)  WE NEED A SPECIAL TRANSLATOR…  ENTER tRNA  SPEAKS BOTH CODON AND PROTEIN, SO IT “TRANSLATES” AND “TRANSFERS” THE CORRECT AMINO ACID

MODERN GENETICS  LET’S LOOK AT IT OVERALL  PROTEIN SYNTHESIS  TRANSCRIPTION  TRANSLATION

MODERN GENETICS  REMEMBER, EVERY CELL IN YOUR BODY HAS THE EXACT SAME DNA…WHY IS THAT?  WE HAVE EXPLAINED HOW DNA ACTS AS THE INSTRUCTIONS FOR MAKING PROTEINS…SO HOW COME EVERY CELL IN YOUR BODY DOESN’T MAKE THE EXACT SAME PROTEINS  DIFFERENT CELLS USE DIFFERENT PARTS OF DNA  WE CONTROLS/DETERMINES WHAT PARTS OF DNA ARE USED?  WE CALL THIS FIELD OF STUDY GENE EXPRESSION

MODERN GENETICS  GENE EXPRESSION IS ONE OF THE MOST COMPLICATED/LEAST UNDERSTOOD AREAS OF GENETICS/SCIENCE TODAY  THE SIMPLE EXPLANATION IS THAT MOST GENES ARE LIKE LIGHT SWITCHES, THEY CAN BE ON OR OFF…WHEN THEY ARE ON THEY ARE MAKING PROTEINS, WHEN THEY ARE OFF, THEY AREN’T

MODERN GENETICS  WHAT CAN TURN THE SWITCHES ON OR OFF?  OTHER GENES  ENVIRONMENTAL FACTORS  **MUST REMEMBER – THE ENVIRONMENT CAN EFFECT GENE EXPRESSION

MODERN GENETICS  UNDERSTANDING GENE EXPRESSION MAY UNLOCK CURES TO DISEASES SUCH AS CANCER  ONCOGENES

MODERN GENETICS  WHAT DO WE DO WITH ALL THIS INFORMATION ON GENES?  APPLIED GENETICS IS NEXT!!