Lecture 20- Biotechnology Flashcards
What is a STR?
A short tandem repeat is a region of the junk DNA (DNA that doesn’t code for anything) where base pairs repeat. Different people have different numbers of repeats at each loci.
What can we do when not enough DNA is present to analyze the pattern of STRs?
PCR, or polymerase chain reaction.
What are the three steps of PCR in order?
Denaturation, annealing, extension.
Explain denaturation.
Denaturation is the first step in PCR, which consists of heating up the DNA to around 95 degrees C in order for the two strands to separate.
Explain annealing.
Once the two DNA strands have separated, the DNA is cooled to around 45-54 degrees C so that the primers can bind to each strand. Primers will bind to the specific sequence that we are looking for.
Explain extension.
Once the primers are bound, the DNA is again heated (72 degrees C) and Taq polymerase extends the DNA.
After how many cycles do we have strands containing just the target DNA?
After 3 cycles.
What are the required materials for PCR?
Template DNA, free nucleotides, taq polymerase, primers, and a termocycler.
How can PCR’s production rate be described? What size of DNA fragments can be replicated?
PCR’s production is exponential, and it can be used to replicate strands of up to 10,000 base pairs.
What can be done once the DNA is amplified using PCR?
Electrophoresis can be used to separate the fragments of DNA based on their size.
How does electrophoresis work?
It works by using an agarose gel and an electrical current (to attract the negatively charged DNA to one side). The gel restricts the DNA from moving forward, and so larger fragments move faster than slower one. It thus separates the fragments based on size.
What is the use of ladders in electrophoresis and what are they made of?
Ladders are made of fragments of a known size, and are placed in one row to be compared to the fragments of DNA tested.
