Drill – Biology! Transcribe the DNA to mRNA: TACCCTCGCTAATGG 2) Find the amino acids that are translated from the mRNA. 3) Why is mRNA necessary? 4) What are the sequences of DNA called that are transcribed into mRNA? What are the other sequences called? 5) Challenge: How do geneticists figure out the sequence of DNA?
Video • Play video clips from LAB
DNA Questions! • How is it possible that each cell in the human body has the exact same DNA (except sperm and ova)? • How does DNA replication work? • Who are the key players involved in DNA replication? • What would we need to perform DNA replication in a lab?
CREATE a PROCEDURE! • What would you need to create copies of DNA in a lab? • Write a procedure that includes: • Ingredients needed • Steps needed
Computer Simulation! • Check out the computer simulation and answer the attached questions. • When you are finished compare your procedure with the actual process of PCR!
PCR: Polymerase Chain Reaction • PCR is a simple process of heating and cooling to replicate DNA • Geneticists need many copies (millions) of DNA before they can sequence it. • In every step of PCR the number of DNA molecules will double • If you start with 2 strands of DNA, and double that 9 times, how much will you get? • What if you double it 30 times? 512 1,073,741,824
Steps for PCR: STEP 1: Denaturation 94°C During the denaturation, the double strand melts open to single stranded DNA, all enzymatic reactions stop STEP 2: Annealing at 54°C : Primers bond to specific regions of DNA (the segment to be copied) STEP 3: Extension at 72°C : DNA Polymerase adds nucleotides to the single strand of DNA (making it double stranded) starting at the primers http://users.ugent.be/~avierstr/principles/pcr.html
The Players… • What would you need in your solution to create millions of strands of DNA? • Genomic DNA • Primers • Distilled Water • Extra nucleotides (ATGC) • DNA Polymerase (adds the nucleotides) • MgCl2 to activate the polymerase
Think about the structure of DNA… 3) Why does the high temperature cause the strands of DNA to separate (denature)?
Where does this DNA Polymerase com from? • We use Taq Polymerase in the lab. • The polymerase was isolated from Thermophilus aquaticus a bacterium that lives in extreme heat (near hydrothermal vents) • So this enzyme will work at high temperatures • Why would DNA polymerase from humans not work? What happens if our enzymes become too hot (95°C)?
Take 3 minutes to answer the rest of the questions on the front! • Let’s do problem #1 on the reverse together real quick.
When you finish… • Raise your hand so Mr. Rosenblum can check your work (and give you a grade) • THEN: create a poster showing the process of PCR and what happens in each step. • Show the amplification so that the number of strands double after each round of cycling.
Exit Pass 1) What happens to DNA when it reaches a temperature of 94°C? 2) Explain the process of PCR and the reason scientists run it.