Im pretty fucked i have a sac wednesday morning on Unit 4 Aos 1 and i know jack shit.
Teacher told us to know the proccess of PCR, purposes of gel electrophoresis, how DNA and the gel work together.
Also what is two independant assorting loci ?
If someone could explain all that for me thatd be super helpful.
thanks in advance:)
PCR is an abbreviation for Polymerase Chain Reaction. This reaction is used for DNA amplification; so we have a small sample of DNA and want to make, literally, millions of copies of this sample. PCR is the way to go. This method involves three stages:
Denaturation: The double helix DNA strand is denature, that is, the hydrogen bonds between the bases are broken as the sample is exposed to ~94 degrees Celsius. The bonds are broken and this will leave us with two single stranded DNA molecules with complementary bases.
Annealing: The temperature is dropped significantly and DNA primers are added to the solution so that they can bind to their complementary bases at either end of the single stranded DNA molecules. These primers act as 'starting points' for the synthesis of the new DNA. The primers bind at the 3' end of each single stranded DNA.
Extension: The enzyme DNA polymerase synthesises new DNA strands on each single stranded DNA (that was earlier broken into two) by attaching nucleotides to the exposed complementary bases. The DNA polymerase bases off the primers, and so synthesises the new strands of DNA in the 5'-3' direction.
Gel electrophoresis: This is a technique that is used to separate and identify molecules of DNA or proteins. In your example, it would be DNA observation. Basically, electrophoresis separates different sized molecules of DNA, based on their amounts of base pairs (hence their sizes). This is done by pouring an agarous solution in the container, and inserting a comb into one end of the container. Once the gel has solidified, the comb is removed and a number of wells are created. An electric current is switched on and the positive end is at the far end of the wells, whereas the negative end is at the origin (or starting point, where the DNA molecules are placed in the wells). Now you should know that DNA has an overall negative charge due to the negative phosphate group in the sugar-phosphate backbone. This overall negative charge will allow the DNA molecules to move from the negative end, in which where they are initially placed, and move/migrate towards the positive end, as positive attracts negative. The DNA molecules all move at the same time, however, the smaller the DNA molecule (less base pairs/nucleotides), the farther it will move. The larger the DNA (the more base pairs/nucleotides), the slower it will move towards the positive end. At the end of a certain time period, the relative positions of the DNA molecules in each well can be used to determine the size of it.
Edit: Beaten by paper-back's wonderful explanation.