- WELCOME TO NUCLEIC ACIDS PART FOUR.
IN THIS TUTORIAL WE'LL GIVE A BRIEF INTRODUCTION
TO GENETIC MUTATIONS. LET'S GET STARTED.
ALL RIGHTY. SO WHAT IS A GENETIC MUTATION?
IT'S ANY PERMANENT CHEMICAL CHANGE
AT ONE OR MORE NUCLEOTIDES IN THE DNA SEQUENCE
THAT AFFECTS THE PRIMARY STRUCTURE OF A PROTEIN.
SO WE'RE GONNA FOCUS ON TWO DIFFERENT TYPES OF MUTATIONS.
THERE'S THE SUBSTITUTION MUTATION, RIGHT,
WHERE WE'RE GOING TO SUBSTITUTE A NUCLEOTIDE LIKE VALINE
FOR ALANINE SOMETHING LIKE THAT.
THE OTHER ONE IS BASICALLY WHERE A FRAMESHIFT
AND THIS IS WHERE WE HAVE--WE DELETE A NUCLEOTIDE, RIGHT,
SO IT GETS LOST, THE LOST NUCLEOTIDE. ALL RIGHTY.
SO LET'S SEE IF YOU CAN RECOGNIZE THE DIFFERENCE.
SO HERE WE HAVE THE DNA TEMPLATE
AND THEN HERE WE HAVE THE MESSENGER RNA STRAND
AND SO HERE IS OUR POLYPEPTIDE SEQUENCE
AND NOW WE'LL LOOK AT "A" AND B.
ALL RIGHT. SO WE SCAN FOR A DIFFERENCE.
AND AS WE LOOK ACROSS,
AS WE SCAN, WE SEE MATCHING, MATCHING, AH, VOILA,
AND THERE'S A LITTLE LINE THERE TO HELP US, RIGHT.
SO WE NOTICE THAT EVERYTHING IS THE SAME EXCEPT THAT T--
THE T HAS BEEN REPLACED OR SUBSTITUTED, ALL RIGHT.
OH, ACTUALLY, IT REPLACES OR SUBSTITUTES FOR THE G. OKAY.
AND SO THEN WE KNOW--
WHAT HAPPENS THERE IS THAT WE ALANINE
AND WE END UP WITH ASPARTATE. SO IT'S THIS AMINO ACID RIGHT HERE.
SO NOTICE WITH THE SUBSTITUTION
THAT EVERYBODY ELSE REMAINS THE SAME.
AND IF WE LOOK AFTERWARDS, THE LEUCINE MATCHES.
SO HERE, THERE'S-EXCUSE ME,
THERE'S JUST ONE AMINO ACID
THAT HAS BEEN REPLACED OR SUBSTITUTED.
NOW THIS LOOKS VERY DIFFERENT FROM THE FRAMESHIFT.
SO ONCE AGAIN, WE'LL FOCUS ON THE SAME NUCLEOTIDE.
HERE WE SEE THAT THE FIRST PLACE OF DIFFERENCE
IS THE G IS NOW AN "A"
BUT IF WE CONTINUE WITH THE PATTERN WE SEE
A, A, A, T, A, A, A, T, G, SO WE--
THIS IS AN EXAMPLE WHERE WE LOST G, RIGHT?
SO THAT CREATED THE FRAMESHIFT.
AND THIS ONE HAS MORE FAR REACHING IMPLICATIONS
BECAUSE NOT ONLY DOES IT CHANGE THE CODON SEQUENCE
FOR THE AMINO ACID WHERE THE FRAMESHIFT OCCURS,
BUT NOW NOTICE THAT EVERY AMINO ACID AFTER THE FRAMESHIFT
WILL ALSO BE CHANGED. RIGHT.
SO THESE ARE THE TWO TYPES OF GENETIC MUTATIONS
THAT YOU WANT TO BE ABLE TO RECOGNIZE
AND SO REMEMBER SOMETIMES THIS CAN GET, KIND OF,
CREEPY TO THINK ABOUT.
BUT REMEMBER THAT THESE MUTATIONS ARE MINIMIZED
BY THE FACT THAT THERE IS MORE THAN ONE CODON
FROM MOST AMINO ACIDS AND THERE IS EDITING
AND DOUBLE CHECKING THAT TAKES PLACE THROUGH OUR BIOCHEMISTRY.
SO DNA MUTATIONS CAN CREATE DEFECTIVE ENZYMES
AND, SO, EXAMPLES OF MUTATIONS THAT WE CAN LIVE WITH ARE,
LIKE, SICKLE CELL ANEMIA
OR EVEN PEOPLE THAT ARE LACTOSE INTOLERANTS, RIGHT.
SO WE--PEOPLE WITH--THAT ARE LACTOSE INTOLERANT
DON'T HAVE THE ENZYME TO BREAKDOWN LACTOSE, RIGHT?
BUT THAT'S SOMETHING THAT WE CAN EITHER AVOID DAIRY PRODUCTS
OR TAKE ADVANTAGE OF LACTAID THAT KIND OF THING.
HOWEVER, SOME DNA MUTATIONS WE CANNOT LIVE WITH,
AND BASICALLY WHAT HAPPENS THERE IS DEATH,
AND OFTEN THIS DEATH HAPPENS BEFORE WE'RE EVEN BORN.
AND, SO, JUST TO WRAP UP HERE,
SO, MUTATIONS CAN COME FROM A VARIETY OF FACTORS.
THERE--WE CAN HAVE THAT PREDISPOSITION IN OUR GENETICS.
THERE ARE CERTAIN CHEMICALS THAT WILL TRIGGER MUTATIONS,
HIGH ENERGY LIGHT, UV, X-RAY, AND GAMMA RAYS.
SO THAT WRAPS UP OUR TUTORIAL ON GENETIC MUTATION.
SO PLEASE TAKE SOME TIME NOW TO WORK A FEW HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING.